I had a very similar situation. I went from a £10k/month family budget to living on basic universal credit. I knew I had no financial security (unmarried SAHM) but buried my head in the sand in the hope that things would either get better relationship wise or that he would do the ‘right’ thing if we split. As it happened he did not do the right thing and walked away with his millions and left me as the primary carer for three young kids, having not worked for over 10 years. I had no idea how we would cope, but we totally did, and 5 years on we are so much happier.
At the beginning it was during lockdown, so I couldn’t work immediately, but as soon as could I got any job I could (worked in a cafe, then started cleaning). It was tough and there were some weeks where I would go clean a house to get paid my £30 cash to go straight to the supermarket for food for dinner that night/week. But I retrained, and am now working for myself and much more financially stable.
Obviously the food shop took the biggest hit. Mindfully choosing low budget options, making meat stretch further, buying basic fruit rather than endless berries. Shopping moved from Ocado to Aldi. Had a big talk with the kids and explained things would be different and we couldn’t have all the treats we used to have. They adjusted really easily to this. I also saved a bit every month for their birthdays and Christmas so I cousins still buy them presents without having to starve that month. Their dad is still wealthy so they have their fancy holidays with him, plus meals out/takeways/expensive day trips. We live a more simple life. Finances are better now, and we live a happy life, just not a luxurious life, which turns out for us, is a more fulfilling one.
The best thing to come of it was the enjoyment we found in the simple things. I got to know my kids so much better. Previously weekends were filled with expensive activities, where the kids were constantly occupied. Now it’s board games/cards/film nights/walks/trips to parks etc. Proper time, chatting/bonding rather than just numbing the mind spending money. What I’d call a more authentic existence. My friends gave no shits about my reduced budget, they were totally supportive and did whatever I could afford.
The point for my little story is; I did it, it was scary and I worried I’d never get out of that hole. But actually it wasn’t as bad as I thought it would be. Lots of elements were really beneficial in many ways. We’re happier because of it, and lots can change. 5 years on I have a new partner, we are married, I’ve sold the house I shared with my ex and we have a house together now. We have an extra baby and blended family. We live modestly but not on the breadline and things are pretty great. Hang in there! Sounds like you have your head in the right place and a relalistic attitude towards the changes you need to make.