Each of the components you mention are negotiable. Salary, malpractice, noncompete, bonuses, % collections. It’s a bit of a chess game, a good attorney can guide you and if there are sticking points that you or they cannot resolve then you move on. It’s one of the many costs of doing business. You’ll never ever see 60%. Even 50% is pushing it these days. If you want 60%, open your own shop and spend a few years in the red, gain efficiencies, and then 60% is probably achievable.
Most private equity will offer a competitive first year salary, a decent bonus and then % collections thereafter. Depending on location the range will likely be 40-50% (I personally would not sign anything for less than 40%). But the biggest question is percentage of what? You must see their payors, they should be open with you on that. If not, red flag and move on. Good luck, happy hunting.