I would be very wary about cutting down to less than 500 calories per day. That is a 'starvation' diet, and your body could turn to metabolising muscle tissue in an effort to maintain any sort of energy levels.
You need more qualified advice than I can offer. What does your gout specialist say? I have never before heard of it being triggered by such a wide range of foods - although I know very little about it, really! Doesn't it come in a variety of types?
Do you have a dietitian you could talk to? it is possible than you are not eating enough to lose. You need to take in energy to lose weight. If your body thinks you are starving, it will hang on to everything it can. I remember once eating only one mug of soup a day for two weeks, and I lost absolutely nothing! (a long time ago - wouldn't do it now!).
Best of luck, whatever!
Viv