I need to get out of a bad situation and I need advice:?

I have been with my boyfriend for many years, and now I must get out. I have been waiting for him to fix a disfunctional situation with his ex-wife and children, and I have supported him emotionally and some financially over the years, without hesitation. Now, though I am realizing that it's an endless battle and I have been, and will remain, somewhere down his list of people to care for. I do love him but it's not a healthy situation for me and it causes me frustration mostly every day. The problem is that although I know I need to leave him, I don't know how to do that. We work and live in the neighborhood very close to each other and the constant reminder will haunt me every day. I am looking for work away from here and when that happens I will move. I have no family for support and the two close friends I have are wishing and praying that I will see the light and get out. However, I am wondering today as I have made my final decision to get out, should I let him know now, certain that he will attempt to keep me at his side? Or should I just one day get up and leave without notice? It saddens me and I am heartsick that I have to make this decision, but it is necessary for my own mental and emotional health. Please help me decide what to do.