I haven't read through everything, but there's no problem with substrate. We just don't want it to choke or cause a blockage. What I would do is get a good organic soil mix with small particles(no rocks that can be swallowed) and use a few inches of that. Add some springtails, isopods, and a little leaf litter. Looks nice, adds humidity, and keeps the bottom clean. You can also remove the river rocks if you do that. Add whichever plants you like that'll add hiding spots, crotons and pothos should be good as you mentioned. Monsoon seems to break for everyone, no matter what they do, around 6 months. If you can put up the cash for mistkings it's much better. Also I find with the mister, that the dripper is unnecessary. I used a dripper for like 5 days ever and was over it lol.