Welcome! Finnegan is a cute kitty. There's a sticky by Dr. Pierson at the top of the main health forum that has a link to a spread sheet with protein, carb, fat and phosphorous percentages in a ton of wet foods. There's also some notes on recommended numbers. IIRC, under 10% carbs, 40+% protein, phosphorous under 300 (lower for CKD cats).
Home testing is easier than it sounds. I was apprehensive about it and I've been giving CKD cats subq fluids for years! Home testing is required as you need to test for BG levels before giving insulin. Also cats get stressed out at the vet and that can raise BG, resulting in higher numbers.
Many people here use human meters, the Walmart ReliOn Prime is $9, 50 test strips $9 and 200 lancets $3. Before investing in a glucose meter, consider the cost of the test strips. The pet specific AlphaTrak test strips are $1 each. In a month, I've been through 100 test strips and haven't tested all that much as my cat seems to be in remission.
You can set up a signature with info about Finnegan. You don't mention what kind of insulin you are giving Finnegan. There are several varieties and they work differently.
There's a ton of info here. It will take time to read through it, reread it and absorb it. Lots of acronyms and buzzwords used.
Finnegan sounds like he is in excellent hands!