It is really hard when more than one area of your life is stressful at a time. It's difficult to disentangle what's making you unhappy, and what if anything would improve things, and it feels like there's no safe space to retreat to to make a decision.
Personally, i think you should avoid SAH while your husband is being unsupportive. It would be very easy to go down a path where it seems to make sense to just have a second child now ('we plan to eventually, there's less disruption this way') and then you know it won't make financial sense to go back so you wait a few more years by which point you're trapped.
Re the job- I've had a situation where I was having friction with colleagues who were being bullying and making unreasonable demands. As it happens, amusingly given the focus on this thread about life coaching, at the time I was having mentoring by a senior woman in my field from outside my organisation. Like you, I loved my job but the people I worked with and the situation they'd engineered made it Impossible for me to perform to my best or even tolerate being there some days.
A few things she made me do which may be useful for you- first, she made me think about what the other people's motivation was. So, for the HOY etc- what is motivating them? What will they get out of it? Is it a personal vendetta against you? Are they irritated at having to adapt to your schedule and think if you leave they'll get someone FT and that will be easier? Is it that they genuinely think that your performance is down but are too lazy/overworked to acknowledge why that might be? Are they adamant on managing you out, or if you improved in certain areas would they lay off?
You're the expert on your own situation, which Is why advice from the outside can be frustrating. I really hated doing what my mentor asked as I thought it wouldn't help, but there sort of wasn't a way out of it and in the end it helped preserve my sanity. If you identify their motivation, it might help identify if there are any options that could help you either continue working there in an improved situation - even if that's just in the short term till you resign - or possibly improve relations so that you get a better reference.
My mentor told me, when I was adamant that I didn't want to try and find new ways to work with my colleagues as it wouldn't help and I had no option but to quit, that it was therefore an ideal learning situation. I knew I was leaving, so anything I tried at that point I could chalk up to learning about people management, safe in the knowledge that even if it went horribly wrong it wouldn't change the ultimate outcome.
In the end, I sat down with one of them and had a v frank conversation. I knew she was ambitious, and analysing her motivation made me realise part of the reason she was so aggressive was fear of Competing against me. I explained my position on some of the areas we were clashing, and that I was only trying to do my part of our job, and not muscle in on hers. It improved things hugely for me- the other colleague, nothing worked, and I did eventually quit. But for the rest of my time there, it stopped being two against one, I could breathe, and do my work. It really made a difference. Good luck in whatever you do, but try not to feel too backed into a corner- there are options even in very limited circumstances.