Wow, a lot to talk about there in those 4 initial questions!
1. Do you see a difference using full frame vs. crop sensor?
The MAIN reason I shoot full frame (and will probably never return to a cropped sensor) is because wide angle is truly wide angle. When I’m shooting at 17mm, it’s truly 17mm, not 27mm.
Secondly, it’s the size of the pixels, like @buddingphotographer mentioned before. The biggerer the pixels on the sensor, the higher quality and better noise control you will have.
Perhaps I can plan to be available Friday evening after the Sacramento Conference Photography Team during teardown to talk in person about these things if you haven’t already upgrade before then. 🙂