Personal 20 Aquascape (looking for suggestions)

[LopezTheHero]

Started my tank a few weeks ago. I'm new to the planted tank, however, I've had an aquarium for a while growing up. I've been stalking the forum for about a year now before finally getting the nerve to start a planted tank.

A little info:
2 5THO elevated above the tank - 4 inches or so
FluVal filter
Fluval 88 GCo2

Plants:
Grosso Stigma
Cardinal Anubis(?)
MyrioFill in the background (thats how I know it, if I could have a ID on the background plant I'd appreciate it).

Fauna:
5 Green Tetras
5 Neon Tetras
5 Cherry Shrip (2 Female, I hope)
1 Bumblebee goby


My concerns:
I just got my Co2 today, and that's after already adding all my fauna. I'm worried I am putting my fauna in danger while I dial in my co2. Another concern, my Fluval co2 is hard as [censored][censored][censored][censored] to dial in. Honestly, a little tap clockwise, a little tap counter clockwise, the bubble counter goes crazy. Does anyone else have this problem, or a remedy to fix it?

My Bumblebee Goby is all alone. I'm not sure if it's driving him crazy. I know he's a brackish fish (didn't know until after purchase, i know, bad purchase on my part, I need to know about this stuff before I bring an animal into my tank). Should I return it or get it a companion?

Here's a small video of the tank. Let me know what you think about the tank, I'd sincerely appreciate it.

20G FLY AWAY

[LopezTheHero]

Pics of the tank: