Unfortunantly, I can't offer much info on the problems at hand, but here's what I can say;
1- The manufacturer, if I'm not mistaking, recommends that you do NOT mess with the mid-range needle, they are factory pre-set and should not be adjusted unless your totally comfortable with tuning an engine. I THINK that the starting point for the high end is 1 1/2 turns out from the bottom, while the low-end is 1 3/4 to 2 turns out, and that adjustment is made with the throttle held wide open, engine not running, of course
2- Generally, you're looking for most ABC engines to run around 245- 260 degrees farenheit. Your engine seems to be a little too rich on the high end needle
3- No clue,
4- A common source for this problem is a bearing that is dry, or no good. You might visually check the bearings to see if they seem like they're hard to turn,or sound like they have trash caught in them.
You might also adjusting the front toe on your car. That will help the straight line ability and also increase the cars steering response. It will also make the car turn a little more in the middle and exit parts of a turn.
Hope that helps...