As previous poster has said those are very high blood sugar readings and definitely will lead to long term problems. He probably will feel quite unwell when he has readings over 20 too.
Going onto insulin isn't an excuse to eat whatever you like though and you shouldn't be increasing insulin to eat more or poorly. The first thing any diabetic needs to change is their diet and reducing carbs will be beneficial, as carbs get converted to sugars by the body. It's also useful to change the type of carbs to complex carbs because they take longer to get metabolised. So changing white bread to brown, white rice to wholegrain rice and so forth. Diabetes UK has a course for helping with the change in diet and I believe that you can get a code from the doctor to be able to access it cheaper or free.
Regarding driving when using insulin, you also need to inform DVLA but also your insurance provider or your insurance won't be valid. There are certain classes of drivers who won't be able to continue their job, purely because they are on insulin. If your husband has a PCO licence this may affect him, as he will need to be demonstrating his blood sugar levels are in control and he's complying with all the testing that DVLA requires. My consultant made me aware that even though I require insulin to be healthy, if I had an accident and hadn't proof of my test results that showed it wasn't caused by low blood sugar, I would be charged as driving under the influence of drugs! https://www.diabetes.co.uk/driving-for-work-and-blue-light-services.html#:~:text=If%20your%20diabetes%20is%20treated,%2Dcarrying%20vehicle%20(PCV).
You will also have to have a conversation with the doctor to give him enough test strips each month, to enable him to do that, as some practices restrict the number of test strips given. A continuous glucose monitor or libre would help him with learning how his blood sugar levels change but you still are required to have a finger prick blood sugar meter to check the results it's giving you. At the moment type 2 diabetics aren't prescribed a continuous glucose monitor, except for those who fit a strict criteria and still many people aren't allowed to get them on the NHS. It doesn't stop you from self funding and there is a free trial to get one from Libre.
If using insulin is going to affect your husband's ability to keep his job, there are GLP-1 medication that may be better for him to try first. One of them, Rybelsus is taken in tablet form.
https://www.diabetes.org.uk/about-diabetes/looking-after-diabetes/treatments/tablets-and-medication/semaglutide#:~:text=to%20weight%20loss.-,How%20many%20types%20of%20semaglutide%20are%20there?,NHS%20to%20support%20weight%20management.
Metformin is known to sometimes cause gastric issues. In many people it's just an unpleasant side effect but for others it can cause an intolerance that progressively gets worse the longer you take it. It can often be managed by reducing the dose but then that would increase his blood sugar levels. In a very small number of people, it causes intolerance to change to an allergy and you can't tolerate It any more.Talk about it when he sees the diabetic nurse and they will be able to assess if it is causing him the bowel issues or if it's down to his high blood sugar levels.
There is going to be a treatment plan that suits his needs and protects himself from the other risks that come with being diabetic. Working closely with the diabetic nurse and discussing his situation and how the medication is working is key. So is gaining knowledge of diabetes, learning about the things he can do to help himself. Make sure you are careful about getting any online education from legitimate sources such as the diabetes UK website.