I haven't seen that type of fugus before, or fungus that grows on glass. Wood etc sometimes grows fungus (as you mentioned) in a newly set up tank and I have had that and it just clears itself given time, as the tank settles and sorts itself out! It ismost likely to be a fungus!
You have been busy, cleaning and treating. All you can really do now is see if it comes back and it will take a while to resettle after such a lot of work. IF it does come bac,k just keep an eye on the inhabitants, I know the fuhgus I had was harmless but I removed the wood as I didn't like looking at the fungus mainly and the second time wasn't as bad so I left it and it just vanished in time as the tank settled down! Even if yours comes back I would just leave it, unless you see deaths of inhabitants of coarse!
Sorry to hear your Betta ate your shrimps, they can be a bad mix. I have had both experiences, the first Betta ate the shrimps, but my latest Betta doesn't show any interest to even the small shrimps, though these shrimps are 'reverted to wild' type so not all that easy to see so maybe he doesn't think they look tasty? There may also be a risk with the cardinal tetras and very young shrimps but you have a densely planted tank so that is good. I had neons with shrimps and currently have ember tetras with shrimps, but they are smaller than cardinals? I wouldn't be too concerned about this, just be aware that you may get less baby shrimps that survive to adulthood, but the flip side to that is you shouldn't get over-run with shrimp?
If the betta is getting another tank I would transfer some of the Amano shrimps into his tank with him. They will out compete the neocaridina for food so you don't want too many in with the smaller shrimp, and anyway it will make the betta tank more interesting to have them a well as the betta and they will help keep his tank cleaner.
Lovely tank by the way.
First post and just signed up to the forum. I have had an electric blue marron since January and he's been going great. But last night I noticed him missing a claw and the other one was limp and dragging. I think he got them caught in the wood in his tank. But the question I have is, the one that's still attached but limp and dragging should I try remove it so the new one can start to grow OR should I leave it as it is and he will drop/remove it himself?