I will this weekend start a new thread with the lineage 17.1 successor of this build and publish a final build here.
You seem to be lucky - I have indeed bought myself a used 7T Pro beginning of this month, so there will soon be a respective thread (this a/b partition thing enforced by G* to all devices initially shipping with 10 is really a p.i.t.a.) . . .
Yes, that is possible - no issues.
There are three options - each of them has their own advantages and disadvantages, depending on the specific situation and setup (the 1st step of all actions should be a nandroid backup of your current setup!):
Thanks for good news. As for your question: extract the FS image and mount it, then grab APK - just like you answered to @zhenev .
I don't know more than you. When you look at their tags (see my link from previous post), it seems that the frequency has improved a lot. I usually look, what is available, when I build the next version to be included in my monthly builds.BTW, regarding microG. I was under impression that you merge quite a lot of patches when you build microg and also that official microg is not being built very often to reflect the changes commited. So the question is: how much does your build differ from official build? Did they start to build more often since project /e/ started submitting the patches? A bit in the dark here about microG current situation. I'd rather keep up with your build extracted from 17.1, not that big of a deal to extract it from time to time. but also wondering if they've sped up their release cycle.
fastboot flash recovery twrp-x.x.x-x-oneplus3.img