One hairy eviction process.. Someone please help!

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I'm in a particularly dramatic situation to say the least. 

Against my better judgement, I allowed my brother in law to move in from out of state with my wife and I. He agreed and was expected to get a job and begin paying rent ($200 a month) after a month. However he has been partying, smoking weed, and chasing tail - with NO money of his own! He claims that noone is hiring but I saw little to no initiative and he began breaking rules I set in the home. 

I gave him an ultimatum, either I give him the processing fee for the 10 day notice and he left in 2 days, or I process it. He wanted the cash and agreed to leave, he signed a contract I typed up and I thought all was good. Until I get word from my wife on day 2 that it was an illegal eviction. He laughed in my face, that day he was served a 10 day notice PROPERLY. I was also given the "greenlight" so to speak to make him as uncomfortable as I'd like during his stay in my home. No shower head in 2nd bathroom, no towels, locked fridge, all canned food stored away, no heat (its NY state btw), no light in the bedroom he's been staying in, I removed the bedroom door as well. Lol I get very creative when I'm angry.. 

It is now day 4 of the 10 day and guess what I found in the snow when I was walking to the front door.... the asshats house key. This is where I need your help guys. Can I legally withhold the key and charge him a lockout fee (like I do to my other tenants) or whats the deal? I dont want to just let him back in if I dont have to... help?