I'm a MS-IV from Ross and juding from my experience and those of my classmates, you should have little problem with matching into a decent psych, FM, or IM given decent boards scores and letters. Probably neuro, too. I think PM&R might be more competitive but I don't really know. Many of my friends/classmates have had interviews at pretty good places. FM still seems wide open and it doesn't look like there's lack of very good programs willing to interview Ross students. According to my classmates, there are still many programs offering prematch positions. Most decide not to prematch because they have their sights set on other programs. Naturally, if you have a red flag in your application, such as having repeated Step 1, you're going to want to do as well as you possibly can on Step 2 and beef up your application in some other way (awesome letters, research, extracurriculars, involvement in professional organizations, going to conferences, etc.).
I'm going for EM myself and have gone on more than enough interviews according to a couple program directors. Am I still worried about matching? Definitely yes. Just don't let the paranoia get the best of you. Going DO is a good option too. But as you've alluded to, it may be a longer road. Only you can decide if it's worth it.