Sorry to hear about your loss
Its good to know that you tried your hardest to care for the fish, even if you didn't have a great knowledge to start with, we all start somewhere and you did alot more than many fishkeepers would.
I'm afraid you can't let him into any water systems as this could (as you thought) spread his illness to other fish. I'd find a nice quite place to bury him, and maybe put some sort of simple marker down as a sign of respect.
You very much did the right thing by coming to this forum and trying to find help for him, if at any point your considering keeping another tropical fish please just come on here and you'll get loads of suitable help.
Anyway, thanks for trying your hardest.
R.I.P Troy