You can take the 4-5 hours trip to the Ban Laem border tomorrow. Go by motorbike or van.
There you will get a new 45 day Visa exempt stamp for around +/- 2000 thb. Plus 500 thb for one day overstay. No-one going to ask any questions and you start over with a clean slate.
Another option is to pay a agent to do the visa extension for you. Expect to pay premium since you already on overstay.
Or you check into a hotel for a couple of nights just to get the TM30 from them and deal with the immigration yourself afterwards.
I would just take the trip to Ban Laem, it takes quite some hours but its stress-free and you also get 15 days extra.
Forget about lawyers, threats, and conflicts with the house owner. Its a losing game and far from worth it. Just let it go.
Continue renting from him if you feel like it or just cancel the booking through AirBnB if you feel like moving on.