Lucky for you, you are applying for the field with the lowest average board scores. Here's my advice:
Do as well as you can on PM&R rotation(s). LOR will be key for you. Show up early every day, ask pertinent questions and read a lot. Stay late. Show that you are doing some reading/research every day.
Take courses, read books, etc, to do as well as possible on Step 2.
Find something about yourself that would make you more appealing to a residency director, and highlight it.
Apply to any residency program that hasn't had a full Match in any one of the past few years.
Get professional training in interviewing skills - it'll make you or break you.
Have several people review your applications before you send them. No typos, misspellings or syntax errors should be found anywhere.
Read the threads here about which programs are top tier. Don't waste your time and money applying to those programs. Apply to every other program. Be ready to travel a lot and with little notice. Take out loans if you have to.
This one is going to insult a lot of people, but it's based on the human nature of the Match process: figure out which residencies have had higher #'s of DO's and international medical grads in their programs. Being a US MD grad, you are statistically more likely to match into a particular program than a DO or IMG. Most programs favor MD over DO, and in turn DO over IMG.
Ok, go ahead and blast me that a DO with good scores will be chosen before an MD with bad, same thing for IMG, but the truth is, program directors and chairs want US-trained MDs in their programs. The dirty little (not so) secret in PM&R is that the IMGs are usually toward the bottom of their rank lists, and are used to fill spots that don't get filled by US grads.
Basically, there are less US grads applying for PM&R spots than there are open PM&R spots. Odds a re in your favor to get in somewhere. It won't be RIC, but it sounds like you'll be happy just to get in anywhere.
Good luck. We're here to help.