Co-parenting arrangement - what’s best for the kids?

My co-parent and I are trying to figure out a system that is going to work best for us and the kids.

We currently have a nesting environment where we all live in the same house but my ex husband and I don’t feel like it’s working for us living together and we want separate living.

Backstory: He moved to San Francisco USA for work, while I stayed in Vancouver Canada with the kids, he cheated (not the first time I forgave the first time and stayed together) we split after this recent time, then about half a year later of having the kids only seeing their dad once in awhile and me struggling being a single parent. We decided to move to San Francisco with him. We all live in the same space currently but it’s not working. I’m 32F he’s 36M, and we have a 9 yo girl, and 3yo boy/girl twins.

It’s damn expensive here and frankly we can’t afford separate living but he wants to get a 1br or studio apartment and wants me to do the same and have us rotate the kids out on a 4-4-3-3 schedule.

I want stability for the kids and for them to just have their own home. So I want US to rotate. I ideally want to move back to Canada, my parents have a basement suite I’d like to have that be the kids home base and me and my ex get our own living arrangements with roommates or whatever and we rotate in and out on a 4-4-3-3 schedule. Currently my ex is not up for that because he wants to stay in the US. Trying to accommodate that I’ve offered that he gets an apartment that is the kids home and I get a roommate and rotate in and while I’m there he stays at his friends place (I don’t know anyone here yet as I’ve just moved here so staying with friends isn’t an option for me). My ex is not into that idea either and insists that he just wants our own spaces and is fine with the kids having to rotate in and out.

How important is that stability for the kids? And is it more important for them to see both their parents regularly or feel like they have their own home space? Because I’m considering just moving back to Canada and staying with my family with the kids and having him visit whenever he wants to just so the kids can have a stable environment but I don’t know what would be better for them.

Thank you for any advice it is really appreciated 😭🙏🏽