Welcome Daffodil8!
I read your story and it was like reading my own from a job I had at one point; it brought me so down with fear and sadness, and yet it was hard to walk away from for the reasons you describe. I have learned the hard way that life is too short to feel that way on a daily basis. Begin looking for another position and line something else up. The devil you know is not necessarily better than the one you don't and you will feel better that you are doing something about the situation by looking for a better match.

You seem like a responsible person, but you do not owe him; you only owe you something. You owe it yourself to take good care of you because no one else will. Find some place or doing something where you can thrive instead. It will make all the difference and is worth stepping out to look for in the end.

Meanwhile, hang in there and when the time comes to quit... yes, you have a verbal agreement to stay until whenever, but plans change. You can just say you have appreciated your position but an opportunity presented that I must pursue, here is my (how much) notice (in writing). If probes further, can always remind him, that this was meant to be a temporary position (need something more stable and/or in line with career goals.) ((((((Daffodil8)))))))