I say you should cut those pumpkins. I harvest mine a week or so after they turn orange, but that is because I like having pumpkins all times of the year. I don't mind if I have pumpkins around the house and it isn't even fall yet.

I have found that like many things the more you harvest the more you get. For instance I had one vine that had only one pumpkin and the rest of the vine was dying there was NO lush green growth just pale yellowing or sick looking leaves but a week or two after I picked it two spots on the vine began growing like mad and now I have two more pumpkins on the vine that I thought was done for the season.

And the "white mold" is more than likely powdery mildew, a common problem. You can use a fungicide if you want, I tried one this year and it works but in my opinion it is more of a hassle/danger than it is worth. On most of my gourds and some of my pumpkins the old and less vigorous leaves have powery mildew on them. And it will eventually kill the leaf but normally the growing tip leaves remains disease free as long as it is vigorous. It has been my experience that the vines have already produced a lot by the time powdery mildew hits so I normally don't bother battling with it. The powdery mildew won't rot your pumpkins if that is what you are worried about. You already have 9 or 10 pumpkins and it is getting near the end of the season, so if more pumpkins don't set in the next couple weeks that is all you will have this year.