Op I'm so sorry you're going through this. Your feelings are completely valid and it's understandable you feel so low and like you need to escape. It's also understandable that you didn't react with happy happy smiles and gratefulness when your husband 'tried'. It's been a long standing issue that wasn't going to be fixed by him trying to woo you for once. He's to blame too.
There are lots of option open to you, many are long term but for now, try to focus on the positives in your life, write a list or think it through in your head and work out what your priorities are and what you want to change. Try not to think too deeply about negatives- see them more as things that need to change.
While your DC are out put a film on or do something to keep you busy. Be kind to yourself, have a cuppa and some biscuits or have a lovely warm shower. Try to distract yourself, even if it doesn't work it's nice to have something to focus on while you think, or some background noise. Doing something routine such as painting my nails, sweeping a floor or folding clothes really helps when I need to clear my head, it may help you too.
Your long term options depend on how financially secure you are and your support network.
You first need to speak to your GP asap to seek support for your mental health as it's decline will effect your ability to think clearly and make sensible, safe decisions.
Then your options are make a plan to leave your husband (which requires you to be financially stable, have a support network for childcare and emotional support and a plan of where you'll live and how you'll fund your life.) Do you work? Do you have a support system?
Your other option is to be completely open with your husband and voice every concern you have. This could be in letter form if you find it difficult to talk to him without arguing or becoming upset. Tell him what needs to change to make you happy, and ask him what you can change to make him happy. This may mean compromising and telling your MIL she can visit the children in an agreed space at an agreed time once a week. Tell your husband you'll be seeking help from the GP for your mental health if you feel able, it'll likely be easier to tell him in advance rather than him finding out.
It's okay if the house is a mess, get your kids tidying their toys when they get back and when you feel up to it you can crack on with small areas while listening to music or watching a film to make it easier. I've been in your situation where cleaning and tidying seems impossible but I found watching a film really helped, it meant I could take breaks and focus on the film for a bit and then carry on. If it takes 3 hours to tidy and hoover one room, that's okay.
Samaritans are great to chat to, even if you aren't feeling suicidal in that moment. You don't have to be religious to speak to them, and they won't push anything on you. You can end the call at anytime if you don't want to talk anymore.
Be kind to yourself, you're doing your best and you will be okay, OP. 