As someone who works on a weekly dancers here in London I can suggest you need to break down the biomechanics with your physio/pilates/gyro/ballet masters.

The long history means that you are fundamentally performing an action that you just don't have the facility to do with the correct motion. Repeated attempts x 000's will lead to a problem. Surgery will not fix any issue it will merely postpone it again for a while. And if the surgeon is removing and labral material that 'adds' to the stability then this could resolve the pain but make things less stable thereafter?

I know it's a real pain in the backside but perhaps you need to take 12 months and break down your strengths and weaknesses and work one on one with a good ballet teacher outside of whatever else you're doing. As you know a clunking hip is pretty normal in ballet, perhaps due to excessive movement that the body isn't really designed to do. As 20yrs old you have the luxury of having time on your side to put this right but you need a good team around you. Perhaps get the physio to come to a class and do some videoing so you can look at the mechanics.

You can read more about this condition here Wikipedia reference-linkSnapping hip syndrome. Note the fact that this is sometimes the psoas rubbing over the anterior inferior iliac spine. The shape of the pelvis is therefore a potential genetic risk factor that we can't do much about.

Also perhaps some regular deep tissue work on psoas etc might assist the whole process. Unfortunately much of this will come with $$ attached and I know dancers have not much of that