Well I'm not DIR and someone correct me if I'm wrong but don't they "encourage" 3 man buddy teams? So this guy that didn't want to dive with you and your husband as a third buddy definitely sounds fishy to me too.
As far as insta buddies are concerned I cringe at the thought of being paired up with one but sometimes I have no other choice. If I'm traveling alone and they have a "no solo" diving rule then I'm forced to be someones' insta buddy and they mine or not dive. I usually end up with someone who thinks they're in a race or something and never sees half the critters they swim over while sucking up most of their air. One guy missed a "huge" Nurse Shark right underneath him and looked annoyed when I pulled on his leg to point it out to him. I had to point at it 3 or 4 times till he finally saw it.
I never ask what their certification level is (I've seen too many accelerated course DMs) but rather "how many dives" they have and how they are on air. Then I usally ask them where they have been diving and by then I usually have a good feel for what kind of dive it"s going to be.
I was really fortunate this last time I had to be an insta buddy and got paired up with a guy from England who had about the same number of dives as I have and as I found out later was also a DM and Tech Certified. So he was a little (read alot) better diver than I am but more importantly our air consumptions matched. We were in the Keys doing a couple of the popular wreck dives which have some depth so we were able to maximise our bottom time. We dove together for 2 days and I have to say he was the best insta buddy I ever had.
So my advise is don't turn down a diver in need right away (hey, it might be me) until you feel them out. It's they who are joining you so if they're not agreeable to the dive plan just tell them thanks but no thanks.
Great advise Jim.
John