Andrey, you look strong and determined to hold your own out there.
Here's my suggestions:
You're playing in an over 30 men's adult league and you'll be facing a variety of guys who can and can't hit. Your main concern should be to get it over, a high percentage of strikes anywhere you can, and get a feel for the game being that you've been away from it for a while.
In your video you're pitching off a flat surface and the distance that your backstop is from you looks far away. At that, you seem to be nailing the guy dead center. Keep that focus.
When you start pitching on a public field you're going to run into all kinds of surface problems that'll take away your balance and momentum, so be ready for it. Do the best you can and don't try and howitzer the ball down to your backstop. Focus on simple strikes, wherever you can get them.
You look like a husky guy that has power. This is a good thing BUT it can be your undoing if you don't temper yourself. Because of the variable surfaces that you'll be pitching off of, your pitching arm will bear the brunt of your pitch. Regardless of the .. "do this...do that", you're going to have to muster enough velocity to your pitch to represent yourself in a decent way - ** according to others** ... so again, temper your aggressiveness.
As this season progresses and you gain in experience of being on the field again, give yourself time to adjust to the games tempo at this level, and at your age. As we get older, the mental gears are whirling away, and sometimes the body doesn't shift gears at the same speed. So, just pace yourself and get that feeling back again of playing ball. Once you have that new influence of this game, you'll have a much better benchmark to absorb and rationalize opinions and suggestions on form, progressive movements and so on.
Finally.... WELCOME BACK TO THE GAME.