Carb problems

An insulating spacer between the intake and carb will help a lot if it doesn't already have one.
The idle problem could be that the return spring isn't strong enough, or the throttle blades shaft/carb could be worn out.
(could be binding linkage parts also)

I'd start with these possibilities and see where it goes from there.

The burned paint around the choke area is probably because of the exhaust crossover in the intake.
The hot exhaust crosses from one side of the engine to the other to warm up the intake for cold climate warmup.
These ports in the intake can be blocked to stop the heating of the intake, but the intake has to be removed to do it.

You may also want to make sure the crossover valve in the exhaust manifold is opening, because if it isn't it will make the hot exhaust flow under the intake heating it all the time. (causing carb boiling)

Just some places to start looking and thinking about.