They can also lock you out for 'fraud' such as starting the game twice on your pc for split-screen multiplay, running some Wine fork or virtualization that they see as anti-theft circumvention, and so on.
By "fraud" I meant: buying a game with a stolen payment method, that's it. If someone does that, the specific game gets removed from their account and this message[1] is shown. The rest of their account remains untouched.
About the rest of your scenarios: They don't look at how many times you launch a game (I launched 2+ copies of a game many, many times). If a game bans you for whatever reason -- like anti-cheat misdetections -- the multiplayer-only ban is only for that game and done by the publisher (not Steam). You're confusing Valve/Steam with EasyAntiCheat, BattlEye, etc.
Steam doesn't even phone home if DRM fails, the game just doesn't launch; DRM meddling doesn't get you banned or anything.