Hi and welcome Nathan!
Lots of questions here... many can be answered with lots of reading from the knowledgebase here:
www.reefsanctuary.com/knowledgebase
You can definitely do some more user-friendly filtration techniques to get rid of the nitrate issue. First step would be to get some live rock. At least 200 lb. for your tank. After the live rock has been in there a couple weeks, start pulling the bioballs out of your sump slowly until there are none left (I'd say over a couple weeks).
You won't be able to keep many inverts with the fish you have. The angel and butterfly will most likely eat corals.
79 is not too hot, it's actually a pretty good temp as long as it's stable.
As far as live sand and plenums and such, I think you should focus on getting the live rock and pulling the bioballs, then think about your next step.
A famous quote for you:
"Nothing good ever happens fast in this hobby."
Go slow, make progress, read, read, read, and most importantly, enjoy!!!
Travis