You need a "recap" post of what you have done from start until now.. 25 pages is a long read.
Have you tried back to back near 100% water changes? I would try that on a 30G.. get a 50gal bag of salt and do 2 25G water changes 24 hours apart, each time putting a powerhead against the rocks to blow out as much as possible to get it into the water column right before the water change. If it is a bacteria bloom due to excess, then blowing out the rocks then siphoning out 25G and replacing should reduce the amount quite a bit, do it 2x in a row and I would think it could be down to manageable levels.
One way to tell if it is a bacteria bloom, does it leave a white sticky film residue on the glass? Not talking about the algae film which is more like a dust, bacteria is sticky when it blooms in a tank.
In lieu of LR?
Everything would be a welcome addition except I don't know anything about gammarus shrimp except a quick google search indicates they are freshwater shrimp?
Its the microfauna I think that will help you balance things out and I don;t think you get that anywhere else except LR and LS.
A diverse CUC is also pretty important so barring the gammarus shrimp go for it assuming the price is ok.
Glad to hear it!
It would absolutely be a good idea to add the critters you mentioned and if the tank is staying clear no worries about getting LR. Really hope the clearness sticks!
Bristle worms are fine. They would need to be a couple feet long to take out a fish,etc. I have several and probably more that i can't see. They are great cleaners capable of getting deep inside rocks.