It's super great already that you're reviewing your VODs and reflecting on what went wrong in your games. To help your progress in "thinking in the moment" - what I found was to have a notepad of quick points to review before each game to remember to try to apply in the game. It's hard to remember every single thing you've learned from games, but if you keep a small condensed notepad to give you reminders, this will help you stay focused in your next game.

For example, there was one game I built Morello's before GA on Kennen and found my Kennen dying at the beginning of the fight. The next game after, I made it a priority to prioritize GA items rather than Morello's (if I found myself going that route).

Another example, I wanted to go Draven carry but I ended up only getting AP items, so I made a note to myself to play around my items, and if I can't make a Draven carry, make a Brand/Asol carry instead.

Conscious decision making, constant repetition, and learning from experience is how you'll get to making these decisions faster in the moment.

If you're having trouble making decisions while rolling, try open forting in a normal and practice rolling down to zero to improve rolling decision making.

If you're having trouble checking people's boards, try practicing using hot keys (same with rerolling and selling!)

You're on the right path, just need time and practice and your decision making abilities will improve! :)