Which side of the rubber

I'm an LHP as well and I throw from the 3b side of the rubber. Not extreme, only my heel is off the rubber when coming set in the stretch, but definitely towards the 3b side. The original reason I started throwing from that side was because I found it easier to locate the ball on both sides of the plate. Since (in general), a lefty's ball has natural tail on it, I agree and I found it easier to throw strikes to both sides of the plate when the arm was "in the middle" of the rubber. I don't know if there is a proper method to it though. To each his own I suppose.

It depends on what you are trying to do. If you are trying to take advantage of a tailing fastball then RHP on the first base side would be typical. If you are trying to get a better break on the curve then the other side would usually work best.

In the end, it is whatever works best for the individual pitcher and that sometimes is a matter of comfort more than anything else.