How do I deal with my husbands behaviors/moods?

We have been together 11 years, married 5. Weve had ups and downs like everyone. But my husband will go through these bad downs every couple months. It seems like if he doesnt get his way or something bad sets him off, hes just so angry at the world he cant function and takes it out on me. This past weekend, we found out our son didnt get into the kindergarten we had hoped for. Dissapointing: yes, end of the world: no. This set him off. He was cold and avoidant all saturday pretty much shut himself in our bedroom all day long and didn't want to talk. But once he gets in these moods, all the problems hes thinking about come to light. So our lack of sex lately (like once a week), his boredom, lack of fun all become my fault entirely. I get the projection of these angry feelings. My best friend of 25 years told me she could really use some company saturday night (her mom is actively dying). So i told her she could come over. I told my husband and said we would make sure to stay out of his way. He then told me how i never make him a priority and was upset. I expressed how he has been treating me poorly all day and has literally refused to talk to me when I've asked several times. I did not think he would care as he didn't want to spend time with me. Then on sunday morning, i reminded him that we had plans to go color eggs for easter with the kids at my moms later that afternoon. He got super annoyed and said he was sick of my family and did not want to go. I said thats fine but i still planned on taking our son as he was looking forward to coloring eggs. He said i again was not making him a priority. When i suggested doing something he liked as well (a hike with the dogs), he immediately shut it down. I asked if there was anything else he'd like to do and he said no and proceeded to ignore me for hours. That evening he tried to explain it away talking about stress and whatnot. I explained i understand being stressed but i don't treat you the way you treat me. I am only asking for kindness. He claimed he can't be blamed for his actions because of stress level. He is constantly up and down mood wise and everyone in the house feels it. Ive tried asking him to get mental health help in a nice supportive way but that ended up with lots of anger and him getting defensive. I truly think he would benefit from therapy and maybe even meds but he won't hear that. Hes threatened divorce quite a few times during his lows. It has made me worry everytime he is in a bad mood that he will want to leave yet again. I feel very little security in my marriage. I have tried to communicate this but it is often met with defensiveness. I feel like he doesnt put much effort in our relationship but expects the world from me. Yes, i have asked about couples therapy but he claims that it would not help. Anyone been through something similar? Any advice?