Well like I said, it all depends on how often you play and how quickly you've reformed :) It could be even a week of playing once a day if you no longer show that type of behavior anymore. I was just stating the average it can take, but it's not a definite number. It all depends on you.
Also, the game audits more than just the 3 games you received on your reform card. It's just to give an example of what not to do that you've done, but it could have been other games in the past that you were toxic in as well that counted towards your restriction.
I do recommend avoiding chat unless it's strictly for gameplay related purposes such as "Let's get baron" or "we should ward more". If you are prone to getting frustrated and typing in it chat it might help calm you down during games if you restrict yourself to neutral chat only :) Or even /mute all at the start of a match so you don't have to worry about others.
Either way, I wish you luck! I hope you succeed in getting reformed and getting your Hextech Crafting back :D