Wow, long thread!
I only got half way through, but had a few thoughts:
As far as epoxy is concerned, has anyone tried Silver Conductive Epoxy? Also available in Zinc I believe. NOT cheap!
As to flat buss bars, I believe in the belt _and_ suspenders technique, always. My CALB cells came with...
I see the original OSB was totally rotted out, most likely a leak caused that. Also it indicates shoddy construction by the manufacturer.
If you check a sheet of OSB at places like Lowes, HD, etc. it will have a painted-on label explaining that it is waterproof on the face and the edges as...