In my experience if a tenant does work for you at your property, you should pay them for their services at fair market value. Most people would probably consider $20 fair compensation in this case. My advice is to tell him you will waive the $20 fee as payment for the bathroom painting as he requested. The reason I suggest that is that if this thing ends up in court, you don't need a dispute over payment for services - especially over $20.
As others suggested you can choose to not renew his lease. The problem is if he refuses to move out, then you will need to evict him. He seems like a hot-head, so I would be ready for either damage or his refusal to leave.
Make sure you send notice that you are not renewing his lease in writing - I would try certified mail in addition to posting on his door. In most states you don't need to provide reason for not renewing a lease and the less you say the better. I would remind him to clean and leave the property in similar condition as move-in for his security deposit to be returned. If he says he is not leaving, remind him that hold-over past the last day would result in eviction proceedings, which will make it difficult for him to rent in the future- not good for him. You want to give him incentive to leave without trouble.
I would call your lawyer and have them ready to serve notice to vacate if he is not gone on the last day of his lease. Hopefully it doesn't come to that. Good luck.
