(Sorry - I'm breaking this into several posts because it's crazy long)
Disciplines: Not going to over-generalize. But, clearly nursing has a slight stereotype for being welcoming of gay men. (But, before anyone jumps on me - I fully appreciate that nursing has been very welcoming for all men, so I'm not trying to generalize... in fact, I might just delete this paragraph because I already regret it). But, from an L & G standpoint, I'd say that (in general, in my experience) that healthcare across the board has been somewhat more accepting than many other professions. Not perfect, by any means, but obviously a many folks gravitate to these fields. [I swear I'm getting stupider as I type this].
Schools: Many med schools have some form of support for LGBTQI students, including interest groups or resources in the student affairs office. My anecdote: I came out during the time between UG and med school, and met my husband at that time (1999-2000). I was in a fairly liberal community, but I was not even out to my family yet when I was applying to schools. But, at the time, I felt like this was a relatively minor factor in deciding where to go to school. [Note, it was still early in my relationship so I had no idea if we were going to be moving together, so I was much more focused on finding the "right" school for me.] I think I assumed that most school would be as open / accepting as my undergrad. But, I also limited my applications geographically to states that I thought I'd feel comfortable in (in general). I'm not from the Midwest, but I did apply to a fair number in the MW as well as both coasts. The other quirk to me is that I was planning on doing an MD/MPH, but I decided to apply to one MSTP because they had a PhD in preventive medicine. So, when I was given an interview at that school, it became more of a tangible issue because the culture is more of an "interview weekend" and people are more likely to bring their spouse / SO. (Similar to residency interviews). I didn't bring him, and I don't recall talking about my "outness" much during the interviews since it was much more focused on research and "would this be a good place for you for 6-10 years". But, they accepted me and brought be back for a second look before I committed, and at that point they were more than happy to let me bring my partner if I wanted. [All of this was reassuring to me, as I didn't know much about the "Midwest" culture, particularly outside of big cities].
I guess I'll throw out, though, that being newly out publicly, I had kinda hoping that it would be a total non-issue with my classmates when I arrived. And, for 90+%, it was. But, I did learn over the years that there were some people who were uncomfortable and/or flat out rude to me and/or my partner. But, there were no "major" incidents that bothered me. And, I also expect that the last decade has changed the culture a lot.
Residency / Fellowship: Again, I think *most* specialties in medicine are going to be fairly welcoming. Sure, psych, OB/Gyn, IM, FP are probably more so, and maybe some of the male-dominated surgical subspecialties are less so, but this is purely conjecture on my part. I was totally out during these interviews, and legally married in my state in 2009 (first round of applications was 2008 (IM) and second round 2013 (preventive medicine)). I don't think I had any bad "feelz" from any programs I applied to, and most offered to opportunities for my spouse to come along if we wanted.
Job seeking: I have been a little more selective in geography now than I probably would have been right after the Supreme Court ruling, because I'm a little worried about certain states' efforts to pass more restrictive laws. But, most importantly (for me) is just making sure that the people I'll be working with on a daily basis are a good match.