s2fmf:
I am impressed. Your dedication to improving your skills should be an example to others.
Here are some of the things I used to do when I was young and had no one to work with at home. Using an old tennis ball and bouncing it off a wall, garage door, or some other solid object. Don't do it the same place every time because you want to get different bounces and it will eventually cause problems if you do it on the same wall or object every time. Work sometimes with bare hands [plural meaning both hands] and sometimes with a glove. Throw it at angles to simulate going for the ball on the backhand {throwing hand] side and going for the ball on the forehand [glove hand] side. At the same time work on different throws to the wall [underhanded or submarine style, sidearm, 3/4s, and overhand] and utilize proper footwork for each possible throw from your position [to first, turning double plays, etc.] It takes some imagination but I think you will learn to enjoy it; I did.
I also learned to throw myself popups by throwing a baseball straight up in the air underhanded. As I gained experience, I could throw it higher and higher and eventually I could put different kinds of spin on the ball to simulate real infield popups. I would work in the sun, away from the sun, with sun glasses and without, in twilight and so forth. I am sure others will have additional suggestions.
Good luck.
TW344