for my ab workouts i do:

russian ab twists with a medicine ball
leg lifts
bicycle crunches
and a combination of a crunch and lifting my legs

For shoulder workout i try to do 3 primary rotator cuff strengthening exercises.

Usually when i throw as hard as i can my rotator cuff doesn’t hurt. Just my elbow sometimes. Are there exercises that strengthen your elbow at all.

Also i do squats(I put my brother on my back and squat him, he weighs about 170) I then do calf raises just by lifting my bro again lol.

I don’t like putting weights on my back just because the bar hurts my back. I don’t know(are their any solutions to this)

But ya thats what i do. I also incorporate long toss and a bull pen at least 2 times a week.