Once you build up the volume of spreadsheet data and show your vet that you're keeping Squallie safe using the human glucometer she'll have a job arguing against it. Vets worth their salt tend to get used to it as time goes by.

At the end of the day, Squallie is your fur baby so you need to be comfortable with his treatment (and his testing method!). You're doing the right things to keep him safe.
7 units BID of Vetsulin is not insignificant dose-wise. As an in-out insulin, it is a little more flexible in use than the depot insulins (Lantus and Levemir) so it can be a bit more straightforward to tweak dosages. You haven't got much test data for evening cycles yet. Some cats run lower at night. I'd suggest posting a new thread asking for dosing advice. If you don't get any replies before injection time, the general rule of thumb here is not to give any insulin if the preshot blood test is less than 200 (ketone tendencies permitting) until such time as one has gathered enough data to know that a particular dose is safe. I don't feel comfortable with giving specific dosing advice (too worried about getting it wrong and something happening to the cat), but I am a naturally cautious person. If Squallie were mine I'd be very conservative with dosing, especially with Vetsulin because it can produce steep drops in BG at onset. I hope that helps you a bit. It's good that you can monitor through the night should the need arise.
I'm about to pass out (I have PTSD-related sleep problems). I hope you'll get additional advice before injection time. All going well, I'll check back tomorrow to see how you both got on.