I would start with a rock rakeBradco 66" Skid Steer, Skidsteer, Rock Bucket, 3" Tine Spacing Universal Skid Steer Quick Attach
You can rent them.
YES SIR I think about that everyday I look at it I'm thinking this will be a good effort and if it doesn't do any
Once you get the majority out, then a powered rake (Harley rake, etc.) will do well. I have used one on the skid steer but I do not think I would start with one with as many rocks as you have.
Have you considered if this is a worthwhile project? Assuming there are just as many buried rocks, they will migrate to the surface every year. You may be fighting a losing battle!
Good luck!