Thank you to everyone for your incredibly helpful insight! I'm feeling more grounded now. I thought I'd loop back and share some of my thoughts for anyone who is working through similar questions...
DH and I especially appreciated the tips on contracting and the alternative tax set-up for UK businesses. Eventually, we'd like to move into a self-employed scenario anyway. Coming back to the UK would definitely enable that transition (thanks NHS!) I shared this info with DH and he remembered his dad (a tech contractor in England) filing with the low salary + dividends method when DH was a kid. Great tip and thanks for jogging DH's memory!
I've done a lot of research on tax implications of porting a US salary to the UK and I think I've got a pretty solid grasp on that now. Not nearly as bad as I was expecting. We wouldn't have any US tax liability in addition to our UK tax liability. The threshold for owing additional US tax is surprisingly high. Additionally, there are ways to become exempt from US withholdings and social security tax on the US income of UK residents, which makes things a little easier.
I did the financial computations as closely as I could - took into consideration taxes, NHS vs insurance, and certain savings (like UK Council Tax being shockingly less expensive than US Property Tax.) If we moved to the UK and kept our US jobs we'd end up worse off by 15k-30k USD every year; but that's not so bad for what we'd gain by living in the UK.
On the other hand, if we moved and took UK jobs (assuming 60k GBP each, which sounds like a stretch!) we'd lose the equivalent of one 6-figure salary for the same amount and quality of labor. I just can't even. I didn't even bother factoring in additional losses from having to commute in the UK, the stress and time commitment of which isn't easily translated to $.
I haven't worked out a UK contracting scenario for comparison yet, but I suspect that would be somewhere in the middle and would include significant non-monetary benefits like being able to continue working from home, selecting our own hours, and generally having more autonomy. As I mentioned above, I'd like to see us in this position at some point.
It was helpful to know what is considered a really good salary in the UK. DH and I had a look at the average UK income and UK income by percentile. Don't know why I hadn't thought of that before, but it helped contextualize the pay rate.
So it looks like coming back to the UK might be worth it, but we wouldn't want to give up our US incomes (just yet). The risk and cost associated with currency exchange is something we'll have to keep in mind too.
Again, thanks to everyone. Additional input is definitely welcome!