Yes, you can call Disney and tell them that you now want to add on more points.
If you have not yet closed, they may be able to re-do your purchase so that you can add the new home resort points to the purchase and end up with better incentives. I have heard of people buying in with say, 100 points at two resorts, and qualifying for incentives at the 200 point level. I would give your guide a call and find out.
As far as resale goes, I think you could also start the process, as long as you have a member #. This way, you can ensure that it goes under the same one (as long as it is the same UY and titled the same way). A different UY or titled differently would result in another membership.
Congratulations and good luck!!!