My husband's overwhelming fantasies

So, about 3 years ago my husband brought up some of his fantasies he'd like to try. It started as Dom/sub stuff and progressed to male chastity. At the time I was grateful he felt safe enough to be open and honest with me, so I did my best to make him happy in that regard. But I do not have a dominant personality, and on top of that my husband has a short temper, and is extremely hard headed, so in our real lives it always has to be his way or no way. We have many marital issues from his temper, that we go to therapy for. But it makes it almost impossible for me to even pretend to boss him around in the bedroom, when I'm constantly thinking to myself "but you won't give in to even the most important things to me?!". The male chastity thing was a bit harder, I had to do research into the psychology of it, and again tried to go along with it even though my heart wasn't in it. Then he brought up wanting me to use a dildo on him, and I complied, but at that point I felt overwhelmed. It bit me in the ass, because then I had to cry to him that it was too much and was messing me up, so he stopped doing any of it.

A few weeks ago though he started bringing his fantasies up again. We just had our third baby, so I'm guessing the hiatus brought it back to the surface. He said he started writing them down in a journal that he wanted me to read. We talked a little bit about them and again I tried to be totally open-minded and supportive. But when I read the journal, my heart sank into my stomach and made me nauseous from stress. He wants to buy expensive lingerie (he's never bought ME any), and wants me to dress and make him up as a "real" woman and take him out shopping and to bars (which we don't even do), he wants us to bring another person (of either gender) into our bedroom, he wants to learn to give head, he wants me to get a strap on (I have since gotten one, again, trying to make him happy), and many more manors of sissification and extreme sexual situations that I simply CANNOT BRING MYSELF TO DO, let alone enjoy.

Lately he has been a real asshole, grumpy all the time, being too stern with the kids, bringing a generally depressing atmosphere to the home. But the only time he perks up or shows me any affection whatsoever, is when he's talking about his fantasies. I only gave birth 8 weeks ago, I had a VERY difficult high risk pregnancy, after a life-altering illness diagnoses, and two miscarriages. I'm feeling super vulnerable, extremely tired, stressed, and depressed. And all I can think of is "why am I not enough? Just me, as his wife?", and I get so incredibly sad. And how can he expect me to fulfill his extreme sexual fantasies, when he doesn't even fulfill my emotional needs?

It doesn't help that our dynamic used to be me wanting sex all the time and him taking or leaving it. Now I have zero sex drive, and on the rare occasion I do feel like I'm going to try to make it happen, he gets mad about something or yells at the kids and I'm like "nope. Don't want it EVER now." And the feeling of drowning in my inadequacies according to his fantasies has me actually terrified to have sex anymore. We have only had sex twice since before the baby was born, and the way I'm feeling now just doesn't show that changing :(

I don't want him to feel ashamed of his inner most desires, I want him to feel secure enough to share them with me, but I just don't understand these extreme fantasies. Honestly, they scare me, and make me a bit sick, but just because I'm terrified that he will leave me because I can't do this for him :( I've explained that I get overwhelmed, and he quickly says we don't have to do anything I'm not comfortable with, but the minute I give an inch, he barrels right on through to try to take a mile, EVERY FUCKING TIME.

I don't know what to do anymore.