I just discovered this project & am over the moon. Have started on a 1/12 scale B-17 myself in order to troubleshoot the 1/8 scale I'm wanting to end up with. This thread is definitely going to be an inspiration for motivating me to get the first one completed. As I've been reading through your struggles, I'm realizing you've faced many of same issues I've run into. Mainly that the complexities which bog things down tend to end up at the landing gear (& for me the engines).
Had the plans worked out 6 months ago but the firewalls & the swappable power modules have been where most of my time/re-dos have been happening. It'll be able to fly on all glow (OS .40s) or all electric or mixed. Which way will depend on what I'm planning on dropping from the 2 gallon/8-chamber bomb bay. If it's just the 2" diameter bombs, then as an electric it will be able to handle the weight of all the motor batteries. I've computed that i don't want the maximum Take-off weight to be over 33 lbs, so if I'm going to drop lots of water balloons, then the lighter glow engines are what's going to be needed. (Hint: Guess how much 2 gallons of water weighs.) The 8-chambers will be selectable as single, double or quad per release. As for the landing gear, while I'm going to build it for the retracts, I'll start out with fixed gear first, just to work out the bugs.
Haven't landed on which scheme I'm going to do it up in yet, but it will be something very different from the usual. Just to turn peoples heads & make them question things, but it will definitely be something that actually existed though. Am inclining towards the German version but also heavily considering a British Night version (All black with brown & green camo on top). Of course, I can't seem to get the "Birmingham Blitzkrieg" out of my mind. (Maybe I'll just make all 3 of them & end up like Col. Jones in Australia. HA-HA)
Anyway, would love to find out how things have been going with your progress. You seem so close to finally having it airworthy. A friend of mine built the Wingspan Models 1/9 scale some years ago (see pic), so I know how large it is. It went in back around 2018, but I just recently found out that he's now working on another one. He has the fuse mostly completed & is now starting on the wings.