If you have power going into the switch and jumpered around it and still dont have brake lights--I would suspect that there is a open fuse or less likely--open filament in the taillight/brake light bulbs. Are you sure that you jumpered around the brakelight switch?? Isnt there more than two leads going into the switch??

Check you owner's manual and see if the brake lights are protected by a fuse and what fuse it is.Then check that fuse and see if it is open.I know that you have already checked the fuses--but replace the brake light fuse anyhow--it is possible that there is corrosion on it.

I dont have a wiring diagram --and it may be that battery wouldnt be standing on the brakelight switch if the fuse was open.And this trouble could be caused by a bad ground on the brakelight circuit.But you said that the taillights work fine--and I would suspect that the taillights and the brakelights would have the same common ground.

Look and check any wiring connectors that run from the taillight assemby back to the cab for battery when the brakelight switch is jumpered..

But first--I would check the brakelight bulbs and check for battery at the taillight assembly--with the switch jumpered/closed and then work your way back towards the cab and brakelight switch.

Does your truck have a trailer wiring connector?