look here for help on the carb.
Motorized Bicycle Carburetor install and rebuild
permalink #16 has info on the needle to make it a little more rich put the clip toward the pointed end to lean it out put the clip to the fat end. wot(wide open throttle is controlled by the main jet and if you look I show the main jet and the stock size to make it more rich you make the hole bigger to lean it out make it smaller. permalink #6
I wouldn't run the bike with the exhaust off if nothing else it will make the neighbors mad.
hope that will help. you might be able to fix your pipe with a short piece of tail pipe/ remake your exhaust that got smashed. If you have a welder or a welder friend with a wire feed or an oxygen/acetylene welder.
You have a very long intake how does it work for you?