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.