What a wanker. Read this and cringed that he's so oblivious.
I was going to jot down the things that worked for me (and still will) but the biggest factor is a husband that's willing to do better.
I really was close to divorcing my DH after our first - I felt so alone and was sinking in PND. (I still don't think he realises how close I was, though I've told him.) Things that helped me move past it - I did a lot of work deciding what I wanted my life to look like. I focused on what made me happy, and ran through different scenarios to see how I'd feel about each one. Sharing custody made me want to scream, so I was committed to finding a way through. It helped that he & I had the same shared goals in life. We undertook a big project together to do with this, when DC1 was a year and a half, that bonded us as well.
I stepped back from parenting a little. Made him step up. If he was doing something wrong, I didn't jump to correct or takeover. I quietly observed and let him figure it out. Your DH should be the one making the second dinner IMO. This was hard - especially if DC was upset. I signed them up for classes together that regularly gave me the house to myself, and gave them a bonding opportunity.
I filled my own cup. Booked PT, time out with friends, classes, etc., Told him rather than asked him, and took the time for myself. Any sass about it was minimal and immediately shot down.
I accepted the fact I will always carry more of the mental load, and compensated for it. He is assigned more of the household tasks - though I'm not sure if he realises yet. I basically assign to dos, and add on a tax for jobs I don't like doing. E.g. I hate sorting car insurance, so he gets double the jobs when I have to do that.
I created a culture of appreciation in our home. I sent him 3 things I appreciated about him every evening. I made him do the same. It killed me sometimes when the things he appreciated me for were mundane - my brain is brilliant who cares I did the dishes - but long term it created more appreciation between the two of us.
I gave us time for connection. Date nights a few times a month, at home, because we had no sitter. Stupid art kits from Amazon, making pizzas, etc., gave him responsibility to plan something once a month at least.
I went to therapy. Lots and lots of therapy. Lots of venting.
I started sleeping again. We swapped nights with DC when they were night weaned - harder because I was EBF. Again, hard to listen to them upset but I was dying of sleep deprivation and they adapted.
I breathed through the fact it was me trying to fix it when I felt he was the one who broke it. I focused on what me and my DC would get out of moving forward as a family.
Today we're very strong as a couple, and it did get easier. But again, he needs to be willing to work - you can lead it but he has to contribute.