Hey bro, good for you for taking this positive step. I saw a study that recently said you have as much self discipline as you believe you have so you can absolutely stick to this.
If you want to remove temptation a little bit more on steam, you can actually permanently remove games from steam following these instructions:
Obviously that won't help for league but try googling if there is a way to permanently delete your league account too.
Good luck with your school focus, go build a great life and game in moderation seeking stories and such. Don't let achievement hunting become a new addiction either, that's a common one too, they don't matter! Just play for fun, story, and not any endless or massive grinds.