Has it always had that mis?
Or did it just slowly get worse?
Or did it suddenly start after you changed something?
You could pull your spark plug and lets see how close your jetting is. Check this link and see how your plugs insulator/tip color compares:
http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html
Wouldn't hurt to give a new spark plug a try after doing that too.
Might be a good time to re-set your valve lash too, everything has had a chance to settled in now so it's probably getting pretty loose with your 18lb springs and all.
You could try some premium gas if you wanna, although I'd be surprised if that's your problem.
I
think your oil puke tank is alright mounted there. But I'm a little worried your clear line might be getting crushed by that clamp where it adapts to your black valve cover hose... You can buy a 5/16' to 1/4" barbed adaptor at a hardware or auto parts store. But... I was thinking it'd be better to just run a whole new 5/16' hose all the way from from the valve cover to the tank. And then just use a short section of your small clear line as a hose adaptor at the tank fitting. That's how mine is set up anyway, you'd end up with just a very short area that's restricted down to 1/4" this way.
That drum brake issue:
Well if those bolts are stripped that sure isnt helping anything... Probably oughta bite the bullet and replace those with some nice grade 8, fine thread bolts with lock nuts. Or better yet double-nut each bolt. (that's where you use 2 nuts tightened against each other to absolutely
LOCK those suckers in place)
I can kinda see why your worried about the rim and over tightening those bolts. I was thinking you could probably install jam nuts tightened up against 1, or both sides of the sprocket. That way you could really tighten up those nuts at your drum without causing any additional stress on the rim.