Continuing along the line of "what do I do in the meantime?"
Appraising my situation, realized that I had available two air mattresses. One was leaking and one was OK to use, but there was no reason that I could not also use the "good" air mattress as well as the leaking one to seal mold. So the other air mattress came into play, deflated, to cover the slightly moldy futon mattress more completely. So I put both of them on top of the moldy mattress, tucked them under the futon so the sheets didn't actually come in contact with the moldy futon and then put bed pads on top of them. This worked for some time, but the two air mattresses moved around over time, despite sticky yoga pad being inserted beneath them to prevent that happening.
Then I happened to be wondering around a hardware store and discovered a "storage bag" for mattresses on sale. The main problem with his solution is it isn't thick enough to exist for very long without getting a hole in it. This implies "painting" or spraying the mattress storage bag to make it more durable. I'm open to using other means to make it more durable other than spray paint - so let's see about using thinking on that idea...
Any suggestions about this?
Another point is, once the futon mattress is inside of the storage bag, it will seal in any moisture as well as seal out air.
So now my other objective is to dry out the futon as much as possible before encasing it in this thin layer of plastic.
Suddenly Danny's idea of "surgery" is starting to look feasible, as is leaving it in a hot, parked car in a dry area for a few days before putting on the plastic outer covering.