First off, if you unplug the toad, do the lights work as they should on the Coach?
With no dash lights, that usually is a sign of a blown fuse in the tail light circuit. You said you checked/changed all the fuses, so I would check the bulbs on the taillights of the coach, it could be a broken filament that is over top of the other filament. I would do all the troubleshooting with the toad unhooked, this separates the problems to either the coach, or the toad.
Get everything working like it should on the coach, then plug the toad in and see what happens.
I see this is your 1st post, so, WELCOME to IRV2.
03 Silverado cclb 3500 drw, D/A, Reese 22k hitch
07 Alfa SeeYa Gold 30RL,2 slides,power everything