On the dragging clutch, you most likely need to dis-assemble it to clean out the rust and lube it, if it is dragging. This may require special tools, hopefully, someone with experience will help. You may be able to improve it by washing it out with brake clean while reving the engine a little with the brake applied. If you do this, you must grease the clutch bearing afterwards, it should have a nipple in the center.
On the back brake, the same thing applies, dissasemble it and clean it, sand the drum if it is rusty and lightly grease the pivots and pins, keeping the grease away from the shoes and drum. This gives you a chance to clean and pack the wheel bearing which it probably needs after 37 years.
I can't quite picture what the gas tap looks like but it is never the threads that seal, it is packing of some kind like in an old fashiond faucet. If you can dis-assemble the tap, you can probably make new packing. If not, you will have to replace the tap.
You are on your own on the pain, although most shops specializing in paint for autos can match almost any color for a price.