It
should be enough. I applied for FLR(M) last summer and my partner and I had similar income to yours (although I also had about GBP5,000 in investments). Everything went fine.
Really, unless you expect your income situation to improve soon, you don't have much of a choice regarding what you apply with. Just send EVERYTHING you have, even your American bank statements; that'll be better than not sending enough!
You might also consider sending a letter explaining that you will be looking for work as soon as FLR(M) is approved, what types of jobs you'll look for, etc. Show them that you're trying to improve your income (without actually saying, "I know we don't have much, but...").
Good luck with your application!
