That is the only way to know that your reservation actually exists. Then understand that he has completely and intentionally stolen money from another DIS member. His call back to your husband does nothing to enhance my confidence that you will actually have a reservation when you finally arrive (unless you get the luggage tags in the mail).
Anyway, I think your only option is to conference call MS with him to at least verify that the reservation exists. I would have absolutely no reservations about contacting him at his place of business, church, or neighbors' house, if I had sent him money and he did not return my calls. And that goes double, knowing that he has ripped off someone else. Heck, you may even want to vist him in person at his place of business - at least he then knows you mean business.
I get a little frustrated when I hear how timid we are when it comes to expecting proper repsect and service. I have rented several times, and if I treated anyone this way I would expect to be publicly "called on the rug" about it - and be sued. You have paid for service and its time to demand it, or your money back!
So demand a conference call with MS. You might also ask your lawyer to send a nice letter to him along with a copy of the contract. Just remember that he has stolen from another DIS member already - so nothing you do should be considered disrespectful.
Thanks for your time. Good Luck - and for any future renters out there, always ask for references.
Brian