Let's try to get back to the truck and stop taking shots.
My only comment on that stuff is the easier a post is to read the more I'm inclined to help. Proof reading before hitting send takes a few seconds.
Regarding your truck:
I just checked the 3rd brake light on the truck and I got to trace down the wires.
I'm losing 12v when I hit the brakes.
Gonna have get the schematic on the wiring to trace it down .....
Can I assume that you mean when you hit the brakes the CHMSL does not light?
They eat bulbs because GM put too much heat in too small of a space. Check the bulbs first. Replacing the 2 578 bulbs with LED's is the only place I'd recommend use of LED's on an S10. To reduce the heat inside the light housing. Prevents melted lenses and burned out bulbs.
Then check the vehicle
CHMSL fuse in the under hood fuse box (UBEC - Underhood Bussed Electrical Center).
The power for the CHMSL goes from the brake light switch thru that fuse, then directly to the 2 bulbs.
Don't be confused by or misled and mess with the CHMSL relay. That is strictly for the extra, not connected to anything, wire in the tail light harness. Which can be used for a CHMSL on a cap or trailer. That relay is over engineering and can be removed with no ill effects to any brake lights. Gm put it there because who knows what some knuckle head might use for a CHMSL on this back woods built trailer. The trailer
CHMSL fuse can be blown w/o any effect on the remaining brake lights. GM engineers win a cookie for doing something right and being proactive for a change.
BTW 58 is not old on this forum. There's folks on here that were in the armed forces when you were born.