I think the advice given was VERY helpful. Did I miss something? Believe it or not, your statements were contradictory.

If your nitrate leves are high, water quality is not good.
Nitrate is a bad thing for inverts. Fish can stand it better, but inverts will suffer. Hopefully your nitrites are at zero, unless you're still finishing a cycle or have begun another somehow.
Also, acclimation of inverts is critical especially if the water ain't right.
I know you may be a bit stressed right now with stuff dying. That's never fun

, but I didn't see any bad advice or condescending tone at all.
Stay in touch with me if you can (or so desire) and let's see if we can improve some things.
Good luck!