I don't know the answer to the first question, as I'm wondering the same thing.
But for your second question - the easiest solution is to modify the "Lateral Acceleration" field in Units. If you want it to turn on a (very large) dime give it a number very close to 0, if you want it to turn in smaller circles, increase the lateral acceleration further.
EDIT - After toying around, I was able to do this fairly reliably by creating a dummy weapon (strafe) which will make your unit behave the way you want it to, while adding a second weapon (legacy) to your unit with an arc of 0 (or whatever you want it to be) with your actual weapon effect and stats. Play around with Options+ and Legacy Options+ for things to work out the way you want them to.
I don't know the answer to the first question, as I'm wondering the same thing.
But for your second question - the easiest solution is to modify the "Lateral Acceleration" field in Units. If you want it to turn on a (very large) dime give it a number very close to 0, if you want it to turn in smaller circles, increase the lateral acceleration further.
EDIT - After toying around, I was able to do this fairly reliably by creating a dummy weapon (strafe) which will make your unit behave the way you want it to, while adding a second weapon (legacy) to your unit with an arc of 0 (or whatever you want it to be) with your actual weapon effect and stats. Play around with Options+ and Legacy Options+ for things to work out the way you want them to.