Really discouraged

I'm trying to be what I'm supposed to be and sometimes I don't know what that is. My husband is very irritable and crabby. He says rude things to me regularly and embarrasses me. If I keep silent, he seems to think I'm okay with it. If I say something, it seems like it's the wrong thing. I'm empathetic and he's not. I'm there for him and he takes advantage of it and bails when I need him. I tired of  dealing with his anger, my own feelings, plus feeling shame for putting up with it and guilt for not finding a better way. I've come to the conclusion that there is no way to help someone else if they don't choose to help themselves. I can be as friendly as I want but if its not accepted or reciprocated, it's pointless. Oh sure, he's nice sometimes. That and the kids are why I stay (plus I don't have a lot of self esteem and doubt I could find anyone now anyway). But niceness shouldn't come and go. If you're mostly kind and loving with a time or two monthly of rudeness, that's just human. It shouldn't be happening every day, several times a day. Case in point. We went to the opera. He'd been looking forward to it but didn't feel good that day. I offered that if he wanted to stay home, I wouldn't be upset. He came along and was basically rude off and on all night long (damned if I do damned if I don't). Then he started in making ugly, mean comments about the breakfast I made. I talked to him and his excuse was "well, I wasn't mean all night long. I was nice sometimes." How do I make it clear that that's not good enough. I feel like a dog on a chain. I feel like I have to find magic buttons to push to keep him happy. I've talked to him about this repeatedly. I've asked him to quit taking his frustrations out on me. Sometimes he seems to do it just to pick a fight. And it's always out of the blue. I asked what I do to bring this on, cause from my end, I think I'm just being nice. He says I'm doing nothing. He just has a bug in his bonnet. Which is all well and fine, but why should the kids and I have to put up with that? Why should we have to feel we've done something wrong. I feel silly putting this in a blog. I guess I should write it privately. I'm just tired of keeping it in the family. I want someone to know how he treats me. I don't want to shame him, but I would like it if someone else heard (besides the kids) and said "you need to treat her better. She deserves it." I'm tired of having no support network. How do you go about finding one? I believe God is giving me guidance and telling me I'm loveable, even though I don't feel it. But I'm losing hope.