Are you using the stock needle or other that is adj. withnothces, if adj. what notch is it set on? A needle set too high will give poor mileage and result in all of theother problems you mentioned. Try using 42/180 jets, adj. needle (use stock spring)with clip set on 3rd. or 4th notch from the top and fuel/air screw 2-2.5 turns out.

 

You also say the idle is still at 850. Why? Did you try adjusting the Idle speed screw to raise the RPM? (not the mixture screw)
You can't get a good adjustment on the mixture screw with the idle that low.

 

not sure on the needle,the idle i set by turning up the idle speed, then the mixture screw in until it seated, then backed out the idle speed until it stumbles.