Don't forget that your brake light switch feeds the signal switch. This means that if you have power at the brake light switch, and follow it up to the column connector, AND if the turn signals work, then you have a turn signal switch problem.
Horns are easy, 3 terminals.
1 terminal to battery
2n terminal to horn
3rd terminal to horn button, which is grounded.
So gorund the horn button wire, if horns work, its the wiring or horn button
If they don't check battery power at relay, jumper power directly to horns to see if they work, and if they do, and nothing else worked, replace the relay