Hello BCCarver and welcome to fishlore.
Well, I surely can understand your frustration. Its a wonderful hobby to get into, can be expensive for sure and when you see fish dieing off, that can be heart sickening. I know how you feel.

I have added a link below for you to check out the topics listed. I believe that it can answer a lot of your questions for you.
Please read up there, and if there is anything we can do to help from there, please post it. I see in your aquarium info that you do not know about the
nitrogen cycle. Its important to have water test equipment on hand, especially when starting out to be able to check the water for ammonia and nitrites which will kill off your fish if they are at toxic levels.
I hope the link will be able to answer some of your questions for you and good luck... please keep us posted and dont give up! We have all faced problems not unlike what you are going through when we started out.
READ FIRST: Freshwater Beginner Important Topics