Well, in general, public schools seem to be the cheapest and their RAships usually waive off some part of the tuition. The opposite is true for Ivies.
I think you have a pretty strong profile. Make sure that you get a good quant score (at least 166) in the general GRE and to satisfy any requirements that the school may have like Calc 1-3 and Linear Algebra. My SOP read like a research statement and I got in, so I don't think it can hurt to have clear research interests as long as they are relevant.
Also, do you intend to go for a Ph.D. after your Master's or industry? For the latter, you can consider borrowing from Prodigy etc. since Biostats jobs tend to pay fairly well.