I finally got things sorted out. I was making bad judgments about this whole mixing process, the kind I think we all make. I worked on these mixes for a while, and I enjoyed the process, and I liked what I heard, so I said "These mixes are good."
Then when my friend suggested I should get a pro to mix the whole thing, the switch immediately flipped. "These mixes are bad!" "I can't release them like this! They don't do justice to the music!"
Blah blah fucking blah. Yes, there are parts of each mix that I would like to improve. Yes, the general character of the Far Side mix is duller and less clear than I'd like it to be. BUT. There's plenty of good in each one. The way that the snares pop out during the second half of each verse in Far Side - I put some thought into that. The balance of the harmonies in the final chorus of La Da Da Dee - I sweated over each .5 dB gradation in each part to get that just right. Sure, I could hand that over to a pro, but he'd have to recreate my creative decisions, or I'd have to live with his.
So here's the compromise. My mixes are neither globally good, nor globally bad. There are good parts, bad parts, and parts in between. Over the next few weeks (it would be sooner, but I'm relaxing this anti-social lockdown I've been under), I'll aim to eliminate the bad parts, improve the in-between parts, and not fuck up the good ones.
I might still enlist the help of a professional, but I'd like to find someone who can come into my studio, listen to the parts I can't fix, and then tell me how to fix them. I think that's much more valuable than having someone do it for me, no?