You always count the date from the first insemination whether doing it natural or AI.
I would take her in for an x-ray to see what is going on with the puppies. It is quite possible in this breed to have a pup with a head to big for natural delivery.
It sounds like with what you observed that she broke her water when you saw the mucous last night. She should have had a pup within an hour of that.
If she has been panting like she was warm she was likely in early labor at that point.
It is safe to x-ray the pups at this age and if nothing else it will tell you if any are in the birth canal position and how many you will end up waiting up for. An x-ray may also show you a big pup blocking the birth canal and let you know a c-section will be needed to save mom and pups.
Check her color to see if she has gums or tongue that look white, blue, or gray looking where they are normally pink, has a slow color refill if you press on a pink area of gum or tongue. If that is going on or she is becoming lethargic and non responsive to you then I'd definitely get her in to see her vet or an emergency vet.
If she starts hard contractions you should see a pup arrive within 20 minutes of full time hard labor and again if not its time to see the vet.
These sites go over the whelping process in pictures and give info on when its time to see the vet
http://www.worldwideboxer.com/birth.html
http://www.dogbreedinfo.com/whelping.htm
http://www.dogbreedinfo.com/whelpingsecondstage.htm
http://www.chihuahualoving.com/Delivery.html
Hope this helps you!

Often a little bit of mucous is all you get when the water breaks.
You can sit with her and put a hand against the side of her abdomen. You should be able to feel a stiffening of the side or a ripple if she is in labor. If its still early labor it may not be very close together so you may have to wait a bit and usually the dog doesn't mind if you do a little bit of a belly rub.
Did the vet check skull and ribcage size against the size of the pelvic opening? If not, if the x-ray was really recent, and the vet office is still open you may want to have them do so.
You can read more about pregnancy and whelping in dogs here
http://lowchensaustralia.com/breeding/pregnancy.htm
Normally labor starts after a big drop down to below 99F then labor begins as the temp starts rising again.

Yes they should have said something to you if they saw an issue.
It sounds like she is nesting which may mean she is just torturing you with prelabor signs :)
You may be up tonight having pups.
My trick to let the mom be calm on her own is to use a baby monitor in the whelping area and carry the receiver with me so I can hear all that is going on and yet let mom be calm and private if she needs that. Some of my girls prefer privacy and some want me right there with them!

Often you don't feel the pups until shortly before birth or not at all. I usually find they are only really easily felt when they are shifting into position for the birth canal.
With the amount of restlessness and panting you are seeing if she does not have the pups tonight I'd go for a second x-ray tomorrow just to make sure all is well. Or you can at least have the vet listen for fetal heartbeats.
The hormones usually leave the vulva expanded.
Do keep an eye on her color and if she seems off head for a vet for help.
Here's wishing you a healthy litter arriving overnight!