Can't retract foreskin much at all. Can forceful masturbation stretch it out better?

Would not recommend. A tight foreskin can be a problem. If you enjoy being "uncut", and depending on your age and sexual practices, you need to develop a routine of attempting gentle retraction and stretching of the foreskin. For hygiene and other reasons, it would be best if you could fully retract and fully replace the foreskin. Do this over a long period of time. If problems, see your pcp or urologist.
Not likely. You should see your primary care doctor or urologist. Phimosis, or inability to retract foreskin, may be a sign of infection/inflammation or even cancer. If you are unable to retract at all, you may need a procedure.