I honestly don't make too much of an effort to raise the humidity... it's usually in the upper 50's and I've never had a problem with a shed. Because you want this one to go perfect, though (and believe me, the first time mine went into shed I was the same way) then you can bump it up a bit right now. You say it's at 70%? Right there should allow for a perfect shed
As for feeding, like you said, go ahead and offer. All three of mine are completely uninterested in food when they are in shed, but I've heard of some that still eat.