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I am not sure why you say that U of T is the top 1 school you want to go, but for biostatistics, U of T is not at the same level as Waterloo/UBC/McGill. Also it is an unfunded program so it wouldn't be hard to get in. I imagine that the admissions at UBC and Waterloo would be more competitive since they are fully funded and have better reputations.

I would assume you attended McGill for undergraduate and master's. If you are pretty sure you can get into McGill's PhD program, it only makes sense to apply to better schools than McGill. With that said, I would not apply to SFU and Pitt. Biostat at Duke and Brown are relatively new and despite their low ranking, it would still be difficult to get in because of their general prestige. Other schools in your list are reasonable targets I think. Given your strong performance in advanced math courses, I think most schools will overlook your D in linear algebra and B- in intro statistics so I wouldn't worry too much about it.

Since you are applying to your own school's PhD program, even if you change to p/f they can still see your performance. I would suggest you go through everything covered in class and do as much as practice you can. If you show major improvement in the final exam, I think you could end up getting something better than a B+. Also a low grade in one course won't kill your application.

I wouldn't worry about your scores. Your scores are good enough for everywhere.

Master's admissions are not super competitive. Since you are from a top school and have extensive math background, I can see you getting into everywhere for master's. You could even get into some top 30s PhD programs given your profile.

Biostatistics is still statistics with more emphasis on medical data. The bio prefix is misleading since biostatistics has little to do with biology. I have not taken a single course in biology and I still did and probably will do research in biostatistics.

Many schools have made the GRE optional this year so you don't need to submit the score if that's the case. For other schools, 157 is indeed too low and I would shoot for at least a 160.

Everyone will go to the best possible school he/she can and most professors would be happy if you end up going to a better school and it's not unusual to apply to many schools.

You could ask your current supervisor at Waterloo if he/she is willing to take you as a PhD student. If your goal is to obtain an academic position then I don't think Toronto biostatistics is a good fit for you. It's a very applied program and the academic placements are pretty bad.

A lot will depend on your undergraduate institution. If you attended a top 5 school in China, with your record, you might have a shot at tier 1 schools you listed and I can see you get into some tier 2 schools. Otherwise, I would cast a wider net. For biostatistics, Waterloo has a better reputation than Toronto. So if you are sure that Waterloo is your safety option, which should be since you did well during your master's, I wouldn't apply to Toronto biostat.

I don't think it necessary to take a gap year to do research. Most statistics PhD applicants don't have meaningful research experience (publishing a paper) so I wouldn't worry about not having research experience. Your have very strong math background from a top school so I wouldn't worry about your grades in analysis and grades in economics won't matter much for statistics admission. I think you might get into a few schools you listed but for safety measure, I would also add schools at the level of Michigan/Duke/Wisconsin.

Your score should be fine.

Some more applied biostat programs might care less about your grades in real analysis so I think you may have a shot at Columbia/UCLA/Emory. I would apply to some programs outside the top 10 just to be safe.

Your low GRE Q, along with B's in real analysis will raise concerns about your ability to do math. With that said, you may have trouble getting into top 10 Biostat PhD programs. Taking complex analysis/abstract algebra is not absolutely necessary unless you are very interested but I would consider taking measure theory. If you do well in measure theory and raise your GRE Q to 165+, I think you have a chance of getting into schools like UNC/Michigan.

You need to convince the admissions committee that you have strong mathematical ability so if you do well in them, it certainly would help. You can apply to some 30-50 range schools but there is no guarantee that you will get in. Even these schools admit very strong international students.

MMF and MQF both have an internship so you pay much less than master's in the US. Those programs, along with top funded statistics programs in Canada are indeed more competitive than most master's programs in the US outside top 5.

Toronto MMF/Stat, Waterloo MQF/Stat and even McMaster stat.

We are not talking about networking here and which statistics program requires networking beforehand? My friends applied to MFE and statistics master's at Berkeley/Chicago/Cornell and ended up getting into most of them. However, they got rejected from funded master's at Toronto and Waterloo.

This is simply not true. You can't extrapolate your experiences to others. I personally know people who got into master's program at Berkeley/Chicago but didn't get into funded master's at Toronto/Waterloo.

All the master's programs you listed are unfunded except for UBC. That said, the bar is not very high and you will get into many of them. Stanford and Harvard may be tough because of their general prestige but they are not impossible. UBC statistics is unlikely but you definitely have a shot at its Master of Data Science program.

Your math background is too thin to get into statistics PhD programs. At the minimum you need a course a real analysis and preferably two. I think all programs you listed are out of reach now. It would be best for you to do a thesis-based master's first because (1) you can secure strong letters through working closely with professors. (2) These programs are generally fully funded. (3) You can take grad level math/stat courses. AFAIK, UBC/Waterloo/McGill have a thesis-based master's. I would take intro to real analysis this term and real analysis II covering metric space next term. If you do well in your intro to real analysis, I think you can get into at least one of UBC/Waterloo/McGill's master's. After completing your master's, you can either stay for PhD or apply to top 20 schools in the US.

Your mathematical background is too light to apply for PhD in statistics. At minimum, you should have done one course in real analysis and many applicants have taken much more proof-based courses. Admissions committees care most about your grades in math/stat courses so your undergraduate GPA won't carry much weight. However, your graduate GPA is mediocre/below average given the grade inflation in grad school so that also doesn't help. With that said, most schools you listed are unrealistic. I am attending one of UBC/McGill and most students are math/statistics major from top universities in Canada or USTC, Zhejiang University in China, so I don't think your odds are good at UBC/McGill either. I would mainly apply to biostatistics PhD programs ranked below 50 since lower ranked biostatistics programs are more applied and more lenient on math requirement. The Biostatistics PhD program at UToronto is very applied and I think you have a chance to get in.

Master's admissions are not super competitive and I think you could aim higher by adding more top schools such as Duke/Washington. I think Michigan is pretty safe for you.

Despite the general prestige of Ivy's, in the field of biostatistics, UNC and Hopkins are perceived to be much stronger than Duke/Columbia/Yale/Brown. However, admissions might still be very competitive at those Ivy's. Your grades look solid and I think if you attended a good school say Emory, you have a good chance of getting into schools like UNC/NC State/Columbia. You could also consider Michigan and Minnesota as they have a very solid biostatistics program. If your undergrad institution is not well-known then I would apply broadly.

If it is optional, then not reporting it should not hurt your chances. For master's program, a 163 is more than sufficient.