Case 1:
What "car" is it? Does your clutch work once the car is warmed up? Can you go directly from gear to gear without the same issues?

Case 2:
I don't fully understand what your problem is. Is your belt on correctly? Are you saying that you think the 2 problems are related? So your timing screw wasn't all the way in and you idled at 750 and you could move to dizzy timing past 18 degrees, then you move the timing screw all the way in and you can't any more? What else did you change when you decided to make your car idle at 1k RPM?