Moving states but away from child for 6 months

I'm looking for advice from anyone who's navigated a long-distance co-parenting transition.

I have two children (6 and 3) with different fathers. My 6-year-old son is autistic.

Three years ago I moved from Washington to Colorado because my daughter's father became unsafe (breaking into my apartment, destructive behavior). My son's father and his girlfriend moved to Colorado shortly afterward so we could continue co-parenting. Neither of us actually wanted to live here.

My daughter's father has been out of the picture since she was 2.

The problem is that Colorado isn't working anymore. I live with my mom, and while she's helping with childcare, we fundamentally disagree on parenting and the situation has become toxic. I've spent years trying to make this work. I've been on Section 8 and affordable housing waitlists, used school and student loans to stay afloat, contacted my church, family, and childcare providers, and worked multiple jobs. I simply can't find a combination of childcare and employment in this town that allows me to support myself without depending on my mom.

My son's dad and I both ultimately want to move back to the Seattle area. The problem is timing. He can't realistically move until the end of 2027 because he needs time to save money.

One idea we've discussed is that I move first with my daughter this fall, get established with housing, work, daycare, and school supports, and then have my son finish first grade in Colorado before joining me either after winter break or after the school year ends. His dad would then move when he's financially able.

We don't currently have a formal parenting agreement, and I wouldn't move forward without getting everything in writing. My biggest concern is being apart from my son for that long, but I also know that stability is especially important for him because he's autistic.

Has anyone done something similar? How did you handle the temporary separation, and what worked or didn't work? Is there anything you'd strongly recommend we think about before making a decision?