Good rule of thumb for ya:
Neos- inert substrate
Cards- ph reducing substrate
Rules can be broken, of course, but this is a good understanding for both.
For my neos, I just use black sandblasting sand from Menards. $8 for 50lbs. Nothing special.
Looks like a detritus worm and nematode. Both are fine and won't harm your shrimp. In fact, it just means your tank is in good shape and developing an ecosystem.
What you have to watch out for are worms with triangle heads. Those are planaria, and (at least in my instance) can attack and kill shrimp.
The most sensitive shrimp that I've had challenges with so far are Malawa in cold weather. The do great acclimating to just about any temperature once in the buyer's house because they are hardy and breed like crazy, but in transit they get finicky coming from a higher temp, and having cold weather cooling off their water quickly.
This:
Expensive, but I'm going on ...um...2-3 years now (?) including take down, drying in oven, storing for awhile, and setting up again- and it's still working.
I'm using remin RO and only 1 bag for a 10g.
Ammocarb is good for trapping ammonia and nitrates from DOA before you can find them and get them out.
My other thought is that the painted reds have been bred and thriving in different params before coming to you. Perhaps you should write the breeder and ask their params?
As far as substrate, I use UP sand and it doesn't leak ammonia. Mine does bring down ph to 5's though, so I use some baking soda to bump it up to the 6's.
Challenge I have is that my water fluxuates during the year from 68-84F. I keep a heater in my Sulawesi tank to keep it 79-80F all year though.
There are many people here who are able to keep their water cool though and would appreciate the RAOK (random act of kindness)!