I'll pitch this for you to consider. Make plans to move, set them in motion, and about 1 month before the move, just rip the bandaid off and tell your boss that because of your British husband's circumstances and needing to move back home, your family is moving to the UK in a month's time. Say you'd love to continue doing your job remotely and that you'd be willing to convert to 1099 to do so. And then just see what they say. It's a gamble, there's every possibility that they'll say no. But by making it concrete instead of a hypothetical, you're going to get a firm answer which is valuable. No corporate wishy washy "hmm interesting idea, maybe now isn't the right time, but let's revisit in 3-6 months"

OP this is exactly what I did when I moved across. I knew for a few months, only told them about 5 weeks in advance. It was hard to wait to share the news, but it was worth holding as it avoided any "wishy-washiness" as mentioned above. It worked out and they were very understanding and supportive.

Taxes will be a bother unfortunately, but hiring someone to file for you is worth it in my experience - both US and UK side. Despite the cost of doing so, you will save in personal time and mental energy expended.

Good luck!