Regardless of board score (which will likely get you interviews), it will be difficult to land a categorical spot. I think like 85%+ of the categorical spots were US grads....maybe even higher. The best advice I have for you is to call programs you are interested in and find out if they hire FMGs (some places won't, so at least then you won't waste money on any of these programs; some places will interview FMGs but may not have ever had one in their program, which also decreases your chance at that program), and apply to programs that currently have in their program categorical FMG residents---these are the programs that are most likely to take you.
Also, consider applying to preliminary surgery spots. If you do well your intern year, you might land a categorical spot at the same program for the following year OR you might get to fill a vacant spot in the program if a categorical quits. Also, you might get great recommendations to help you get a spot elsewhere. Some programs have a reasonable history of hiring prelims into their program, so consider these programs as well to keep your options open.