First of all kudos for getting the data from the vet onto the spreadsheet before Mowgli has even arrived. You've got this and are going to be a great Mom for your extra sweet kitty.
The data from the vet definitely sets off a few red flags for me. A starting dose of 3u is very high for a newly diagnosed cat. It appears they wobbled a bit with the dose initially and the rationale behind the "wobble" is not clear at all i.e. 3u given at a reading of 160

and then no pre-shot reading the following night and a dose of 1u even though it appears likely pre-shot would have been higher than the night before. It also appears they were dosing blindly for many cycles and obviously were doing precious little in the way of mid cycle testing to see how low any particular dose was taking Mowgli.
Insulin is not a medicine. It is a hormone and therefore doesn't behave the same as medicine. More is not always better or more effective and too much insulin can look exactly the same as not enough. Totally counter intuitive and something we see a lot here from vets not understanding how insulin works.
The high numbers Mowgli has had so far could be/likely are from too much insulin. Only by starting at a low dose and slowly increasing can one be sure they have not skipped right over the ideal dose.
Since Mowgli will be in a strange environment upon arrival, he may not eat as well as he usually does and he may be a little stressed out by the travel etc. so I would expect he may suffer a bit of BG elevation from stress in the first couple of days. There is also a learning curve for you to get comfortable testing Mowgli and we have no idea how co-operative or un-co-operative he might be in that regard (I have to wonder if Mowgli had anything to do with the lack of testing at the vet knowing full well any lack of co-operation on his part might have been due to the strange and probably noisy environment). Many of us have cats who come and tell us when it's test time but sometimes it takes a bit of bribery/time to get kitty to that point.
Do you know if Mowgli was tested for ketones or has any history of ketones or DKA? Anything in the vet records?
If not, I think the dose should immediately be dropped to 1u twice daily. If there is a history of ketones or DKA, then let us know and we'll work on a plan to reduce a little more carefully.
I think your main goal right now should be getting Mowgli acquainted and comfortable in his new environment and making sure he is eating, peeing, pooping, preening and hopefully playing a bit. I would not change his diet immediately. Let him settle in for a few days and make changes slowly to avoid any GI upset or general stress.
We advocate testing before every shot and also getting a mid cycle test as often as possible. Obviously you have to sleep so we recommend making it a habit to test before bed every night so that you have some data from the night cycle because a lot of kitties go lower at night than they do during the day.
We have lots of tips and tricks to share to help you get going on this journey and before long it will be a short routine you and Mowgli share that will only serve to bond you and your little fur baby all the more.