To further clarify: anyone can accept a pre-match except US allopathic seniors. DO students, FMGs, IMGs, and anyone who has already graduated from med school all can sign outside of the Match.
As an independent applicant, it is not illegal to contact your #1 or any other program at which youve interviewed that you think is better and make them aware of the situation. I would contact your other programs quickly, and give them as much time as you need to make a decision. Your #1 may stick to their guns though.
There is risk involved in this. This was one of those scenarios behind the rationale for instituting a match. To avoid playing programs and applicants against other. To avoid pressuring applicants into making hasty decisions. Although your pre-match might be a less desirable program, it is only one year, and most of here would argue that we can do anything for a year. You will have some peace of mind for the time being. But the fact that you have that many interviews lined up suggests that you may be more competitive than we thought.
One other thing, if you accept any prelim pre-match offer, be aware that you wont be able to rank categorical PM&R programs.
Tough decision.