PhDinSLP

Yes, my understanding is that it's possible. See the following from a helpful ASHA FAQ piece about getting a PhD:

It helps to have research experience, but I don't think it's necessary. Very few SLP master's students do a thesis. Just try to make the case in your personal statement that you're really interested in an area of research that relates to SLP, since you're from a different field.

It's true that you'll need to find a program that will allow you to pursue certification also, but in my experience programs are very open to this. Getting certification will add a lot of time to your PhD program (you'll probably have to get another master's degree), but you'll come out of it much more competitive for jobs. Compared to psych PhD programs, I think you'll find that SLP PhD programs are much easier to get into and much more likely to fund you. And after you graduate the job market is also much better. Since your situation is unique, I would start by emailing the programs and asking (1) if it's possible to seek certification and the PhD and (2) how they'd want you to go about applying. My guess is that they'll be very responsive--PhD students are much harder to come by than MA students. Also think about your research interests and what programs might be a good fit. If you did a thesis in your last master's, see if you can relate your thesis topic to an area of research in SLP. If you think you're interested, go for it! It's a great field and there's a real need for PhDs.

No, it will not hurt you to have a 4.0. I got into one of the schools you listed this fall with a 4.0, and I know at least one other applicant who was accepted to top schools and had a 4.0. Don't overthink things! At least in my experience, numbers (GPA/GRE) seemed like the most important thing.

You can definitely do a combined MA/PhD. Some schools advertise the option and others don’t. If there’s a particular school you’re interested in that has both programs but doesn’t advertise a combined option, you can contact the department to see if it’s possible. I started my search by looking at the programs that advertised a combined MA/PhD option on EdFind. If you know you want a PhD, there are definitely advantages to going straight through: you only have to apply once, you only have to move once, you’ll be finished sooner (as in sooner in your lifetime), it might streamline the process somewhat (i.e., 6 years instead of 7 total between MA/CFY/PhD), you’ll be working on research with the same mentor for longer, etc. Also, if you apply to a combined program you might be considered for funding reserved for PhD students, and schools usually have more money to fund PhD than masters students. I would recommend attending the ASHA Convention if you can (it’s in November in Denver this year, and you can get your registration waived if you're accepted to volunteer). I did that last year and it was incredibly helpful. I talked to programs at the grad school fair and set up meetings with students at one of my prospective schools. Also check out the resources on ASHA’s website. I'm starting an MA/PhD program in the fall. I also want to teach, and I plan to get my CCCs during the program. If this is the path you want, go for it! The field definitely needs more PhDs.