Welcome to FDMB and so sorry Tabby has diabetes and has had such a scary start to treatment. What a handsome boy he is!!
The MOST important thing you can do is to start home-testing. Especially in the beginning when dosing is just being started kitties can have hypos since it is not known how they are going to react to the particular insulin and the dosage...as you have already seen with your poor Tabby.
You can post of the Main Health Forum:
http://www.felinediabetes.com/FDMB/forums/feline-health-the-main-forum.28/
to get more information on testing and setting up a spreadsheet to track the progress. There have been several kitties on here who had hypos but were able to be caught early because of home-testing.
This page gives an overview of some of the information available here:
http://www.felinediabetes.com/FDMB/threads/where-can-i-find-________.127890/
There are lots of caring and experienced people on this site that will help you with Tabby's treatment plan and any questions you may have.