You have gotten good at knowing what dose is good on what PS. It just takes time and data gathering to be able to start seeing the trends.
A new vial does not automatically call for a dose decrease, it depends on how it was stored, handled and how long it might have been exposed to sun light. That said I would start the new vial on a day you will be able to monitor just to make sure. I used Harley's vial down to the last drop and it was fine with no crazy numbers on the new one.
It makes me sad about our Vets these days, they are either too busy or don't care enough to follow up. My Vet forbade me from home testing and told me to give him 1 unit twice a day and come back in 3 weeks. The next day I found this board and with the help of Sheila Beau & Jeddie by his next 3 week appt. Harley was OTJ and stayed that way for a year. I didn't keep my next appt and she never questioned it and never called about him. To this day she couldn't tell you my sugar cats name and the saddest part of that is, she was my daughter in law for 10 years and is the mother of my grandchildren. So don't feel too bad about your Vet.