First off you were absolutely right to switch his food to the grain free Wellness! Lots of folks use it here for their diabetic kitties. I don't since I have 13 cats only two of which are diabetics and it just doesn't fit into our budget to feed everyone that, so we feed good old fashioned Friskies pate, which got one of my diabetics into remission and off insulin. There is nothing special about the DM except the price and there is far better stuff out there on the commercial market, plus most cats tire of DM.
Secondly great instincts on wanting to test Oliver at home, this is absolutely the very best thing you can do to keep him safe while he is on insulin. Being tired especially in the morning is rather concerning because it could mean that he is going to low and starts acting more like himself once it starts wearing off. The only way for sure it to test him yourself before every shot and getting spot checks in when you can to see how low he is going. You will find lots of tips and tricks as well as some excellent videos here on how to start testing him at home
Home Testing. It can be a little frustrating at first but once you find your groove it gets as easy as brushing your teeth. I can literally now wake up, grab the test kit, test Musette and be back to sleep in 10 minutes.

Not only will testing Oliver at home keep him safe it will also keep money in your wallet. Since he won't have to keep going back to the vet's to have curves run, you can do them yourself at home and just share your data with your vet. As well as giving you truer numbers, since Oliver won't be all stressed out by the vet visit, and stress will raise his bloodsugar.
A shopping list for you for testing at home.
Human Meter that takes a small sample of blood and strips that sip. Walmart has an excellent meter called the Relion Micro, the meter is around $9 and 100 strips are about $40 (the strips are the most expensive part)
Test strips to match your meter
lancets and a lancet device in the beginning you want a slightly larger gauge, normally these are marked as "for alternative testing spots" but you want about a 25 gauge, the smaller the number the bigger the lancet.
Ketostixs to test Oliver's urine for ketones, these should be right next to all the other human diabetic supplies and are pretty cheap as well.
A rice sock for warming up his ears..warm ears bleed better than cool ears. These are easy to make, just take a thinnish cotton sock put about a 1/4 of a cup of plain uncooked white rice or oatmeal in the toe, and knot...easy. Then when you are ready pop it in the microwave for a few seconds until it is very warm but not hot ( I test it on my wrist just like you would a baby bottle). Hold this to his ear for a few seconds to get it nice and warm.
And if you are still having problems getting it down and want some hands on help just give us a general location, city and state and we will see if we can round up a member that lives close to you that can pop in and give you a hand.
Congrats you are now a proud owner of a Sugarcat! And you have landed in the very best place you never wanted to be, but will be so blessed to have found to help you help your extra sweet Oliver. Everyone here either has or has had a Sugarcat that they are treating successfully, some of us even have several
You are off to a very good start, you are on an excellent insulin, and started at a good dose, on a great diabetic diet and wanting to test at home...we can help you figure out all the rest.
Read everything you can here, print out the stuff you want to refer back to, and ask all the questions you want, someone is always around to answer them or at least point you in the right direction to the answer. We never close as we have members literally around the world.
Welcome to the FDMB Family of Sugarcats and the people that love them.
Mel, Maxwell, Musette & The Fur Gang