(It's a gif, but sometimes it gets stuck on the last picture for some reason)
Anyway...about the vet - It's okay not to tell them everything. It's also okay to play dumb sometimes. Like with the dose for example. If he asks why you're at 2.75, just look blankly at him and say "I thought that's what you told me to give him"
And if he doesn't want you to test so much, just don't show him the spreadsheet. My vet never really looked at it very closely anyway, so now I just tell him something like this: "Sam has been around XXX at PS's, and his low numbers are around XX" That's really all the vet needs to know anyway.
You could take a more direct approach and just explain to him that while you appreciate and value his partnership, you feel more comfortable taking the lead on the dosing decisions since you are with Gizmo every day. That you want his feedback, of course, and hope that you can be collaborative in managing his diabetes.
As for the dental, is there a known issue with his teeth? Or it's just time for a cleaning? Vets don't seem to know or believe this, but there is a very clear connection between dental health and BG numbers. So if there is a known issue, it may be difficult to get him regulated until
after his teeth are taken care of. So it might be important to push for the dental to happen sooner and not try to wait. If it's just a regular cleaning, then it's probably fine to wait a little bit.