A few things.
The coolant temps of the engine have little to do with the problems you are facing. There could be numerous reasons some of these things are happening and each will need to be chased out.
Hard starting when warm. How hard? Like crank and crank, play with the throttle and crank some more then it will light off?
First thing. What is your starting procedure? Are you pumping the gas or just hitting the starter and hoping it will catch?
That looks like and Edelbrock 1406 style carb. They are good, but all carbs are a heat sink. Modern gas doesn't like heat, but it's not as bad as the old stuff was. Still, an open element air cleaner, a 200 degree engine, a carb with no heat shields and possibly too high of float levels can make them boil the gas into the intake. If it puffs a black cloud on hot starts without you pumping the pedal, I would be looking at fuel boil over out of the bowls into the vents and flooding while it is sitting there. If it doesn't puff black smoke and you have to crank it 50 revolutions to get it to fire while pumping the pedal, you need to make sure your accelerator pump is working and adjusted right, as well as making sure you are getting full voltage to the ignition system while cranking and that you don't have a weak ignition issue when it gets hot.
What kind of ignition system do you have? HEI's are notorious for heat sink issues with the module. There is also the issue of the intake manifold on that motor. That looks like a single plane intake. They aren't the best for drivability at low rpm and starting ease. If you have points and an external coil, you need to make sure all of that is up to speed or it will be a hard starter as well.
Brakes not Returning:
Sounds like a soft line is collapsing, or you are getting the lines hot and the fluid is boiling, thus expanding, or you have an issue with a hard-part like a proportioning valve or a residual valve somewhere in the system. Deal with the heat first, then you can fine tune into some other areas. Do some research on what others have worked through on braking issues and you may have a common problem that others have identified and fixed.
Brake and Clutch Fade: = Heat
Those are fenderwell headers. They will concentrate heat in areas that Toyota never meant to be hot. They will radiate that heat into the clutch and brake system. Only cure is to either swap them out for a style that dumps out the center away from all those things, or make up some heat shielding and keep the radiant heat away from things. The header wrap will help, but without airflow, and direct shielding, you are still going to have heat soak. I love fenderwell headers, but they do require some finesse to keep the side effects at bay. Manifolds will probably help your issue, but they have drawbacks as well. They can cause lot of radiant heat soak issues in the cylinder heads and you will see a pretty substantial loss in HP and MPG by going back to a log style manifold. You just have to work through the compromises to see what fits your style best.
Radiator Shrouding:
There is a reason the OEM's use a lot of baffling and shielding around radiators in modern cars. You have to do everything you can to keep the hot air from doing a u-turn and getting back into the radiator. Just about the worst thing you can do is hang an electric fan right on the radiator like most people do. Your setup is very typical of a bad one. You are only getting the cooling of the radiator within the circle of the built in shroud on that fan. That cardboard you are putting on there is basically keeping the hot air from getting sucked backward, through the radiator and doing a u-turn, to go back through where the fan is pulling on it. It will help, but it won't fix it like the proper shrouding will.
Nice looking rig. Just needs the typical "un-hotrodding" things done to return the driveability that the oem's spend a lot of time dialing in.
