Skim milk+cream in a cake rather than whole milk?!
Answers:
I think your proportions are perfect. It should be fine - if anything, it will be more moist.
I never tried that, the the cream does have lots of sugar in it..so if you want try to taste it first before you add to batter to see if it taste like regular milk, I'm pretty sure it will come out right ..=)
I do not believe you need to add cream... If I were in this predicament, I would use the skimmed and not worry about it. The amount of fat involved is neither here not there.
That will work fine. Cream normally does not have anything like sugar in it, so you'll have no problems.