>1. Since I'm working inside a sphere, there is no real sketch plane to work with.
How much training did you get with Inventor?
>it doesn't allow for updates to the part if I change my mind about the size of the circle feature.
First thing I noticed is your sketches are not constrained.
http://home.pct.edu/~jmather/AU2006/MA13-3%20Mather.pdf
Why not simply pattern the feature?
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