If his mother has 40+ years experience, then she should be able to take care of all of that and guide you...?
You just kind of have to go with your gut with alot of it.
I realize that emergencies come up, but I can't imagine someone just leaving you to run the show like that. (nothing against
you) Screening potential homes can be quite time consuming, you may want to do in-home visits, have the new owners visit the pups to bond with them first, get references from a vet they've used before. Did the guy leave you any kind of criteria that he uses normally when placing them?