Seems to me you are doing everything right in regards to care for the snake... obviously done a little homework before taken the little guy on.

I don't own Pueblans myself but have a few other ssp's of Milk's and none of them much care for temps beyond 80 degrees... I don't think that's in anyway part of your problem though as you do have a temperature range that is more than adequate.

A regurge at first is not all that unusual but given you say the snake was undisturbed for 5-6 days but still regurged is... I can only assume you were as careful not to disturbed it for a few days after the second feeding attempt.

First question for you is are you certain the snake didn't have feeding issues before you bought it? Second do you notice any unusual bumps/bulges near the snakes stomach... roughly 2/3 down the snakes overall length?

Don't want to knock "chain" pet shops but all too often they simply don't know how to care for some off the exotic pets they sell... toss a pinkie in on a feeding dish and hope for the best... mean will the snake drags off the pinkie through the bedding... ingests a few bits of the bedding along with the pinkie and blockage occurs. Not saying this is the case as there could be many reasons for your snakes problem.

Best advice... make the pet shop aware of your problem... attempt feeding again and be certain to leave the snake undisturbed for 3-4 days... even leave the lighting off. If you think there are signs of bumps/bulges search out a good vet in your area with knowledge of reptiles.

Sorry I can't be of more help but there could be a multiple reasons behind your snakes problem... certainly doesn't sound as if you are in anyway part of the problem though.

Gerry