So today I decided to try to play with things on my computer, disabling one process at a time whenever my practice game vs. bots crashed, to see what might be making it crash.
1. First the firewall (Comodo Firewall Pro free version) went. It made Windows bluescreen earlier today, so I figured I'd just uninstall it anyway.
Still crashed, but it seemed that it crashed when i right clicked and dragged by accident (I posted earlier about how it seemed to happen when I was clicking a lot?), which would have activated my desktop mouse gestures.
2. Disabled desktop mouse gestures (humorously named "StrokeIt" program).
And then I was able to play a complete (practice) game.
We shall see in the future if this really fixed it or if I got lucky. Thanks for keeping tabs on us crashers status, Riot staff. Sorry for complaining if it was on my end the whole time, haha!