What to do to eliminate cold and moisture in Basement

I have what I consider to be a fairly dry basement, although I do have a 65Pint dehumidifier running most of the time, year 'round in the main part which is ~24x27. On an inside wall (walls are all dry-lock-treated block), there is an opening to a crawl space that is below the dining area and family room on the back side of the house.
In the winter, there is a pretty strong, cold draft that sweeps into the basement from the crawl space area (which has a concrete floor, block walls and bat insulation hung from between the rafters under the family room floor).
I thought about installing something that would make that opening to the crawl space closed and also thought about getting up into the crawl space with some spray foam insulation and looking for every little drafty area along the outter block walls but, don't want to do this if it is supposed to NOT be air tight. Could someone please share some advice with me, here? Thank you.
In Delaware

 

Your crawl space either needs to be redone with insultation at least on the walls with HVAC added to be correctly defined as inside space or it should be sealed off (permanent or with exterior door treatment)and then ensure it has outside air venting to help eliminate moisture.