A few comments:
Relax a bit. Your engine runs well! You have a good build there.
Your fuel peacock is good. When the valve is aligned with the fuel line it is open. When the valve is PERPENDICULAR to the fuel line it should shut off flow.
The switch on your carb is the choke. If you have trouble with cold starts, move the choke lever up which denies air to the cylinder. You'll have to turn off the choke for a normal run condition.
Check those fenders! The way you bang over those road humps you could knock a fender loose and crash. You may want to ease over those things s bit more. Come off the saddle or something.
To improve braking, see if you can adapt V-brakes as they apply higher pressure to the brake rims.