Don’t chase your tail and just throw parts at it.
A simple $15 light tester will tell you a lot.
Make sure test light is connected good ground and verify
Then Test for power at brake bulb socket. If power there then fix ground. Remember you need a ground jumping cab to bed.
If no power at socket work backwards testing for power on circuit along the way.
test power in and out of the brake switch.
Test power on both sides of the fuse. Good fuse on a rusted socket is not unusual.
The cheap tester is the best 12v diagnostic tool you can own.
https://www.amazon.com/dp/B07Q3622FT...ZZ5K0Z54VR8JZY
Mark