Hi Blueduck! Nice to meet you!
Here is my take on things, bearing in mind I'm not actually a medical professional or anything close! (if you have a linguistics question though, I'm your gal...lol!)
So as to type, you could be T2 or T1.5. The fact your BGs were up and down doesn't really mean much I don't think. It's true that T1s in general have more ups and downs than T2s. But you were on mixed insulin, and just about anybody would have ups and downs on mixed!
A "regular" T1 would not have been able to survive for 7ish years without insulin. But T1.5 is a slow-developping form of T1 that can look like T2 at the stage where you are diagnosed (so you are starting to lose some of the insulin cells, enough where you have noticeable symptoms, but there are still enough left that T2 drugs like gliclazide that work by stimulating your body to produce more insulin will work on you for a while). Eventually you lose enough insulin cells that those drugs don't have anything to work *on* so they stop being effective and injected insulin becomes necessary.
Trouble is, this can also happen to some T2s anyway overtime. Although it's all a bit fuzzy because a lot of the statistics we have on "T2s" probably include a lot of T1.5s as it's a relatively new "discovery" and lots of people are misdiagnosed at the start and never re-evaluated.
There are two types of tests that can help determine your type. One test (a C-peptide test) checks for whether your body is producing any insulin of its own. This test doesn't tell you everything, because some long-term T2s produce little insulin anymore, and a T1.5 at the start of the process would still be producing some. But it's better than nothing! The other test (a GAD-antibody test) checks for whether your insulin production is being destroyed by an immune system attack. This is a sure sign of T1 or T1.5. Unfortunately this test has a time clock on it, 8-10 years from the time the immune attack would have started. Because once the immune system has finished destroying all the insulin cells, the attack is over and eventually there's no evidence left of it in the body. So you'd have to get this one rather soon in your case! These tests are not very common ones to run, they're expensive so they're not done routinely. You have to ask for them, and you may even have to insist on them / do some convincing to get them. But most of us here feel that it's generally worth having them done, for the peace of mind if nothing else! (see next para)
As to whether or not you need to know what type you are, it's yes and no. Yes, because if you are T1.5, it's a sad state of things but you do actually get access to more supplies and tests and generally a better standard of care. So if you can get access to all of that, you definitely should! But no, because in the end, all that matters is your BG levels. If you can maintain good BG levels with a bit of injected insulin but not without, and you can figure out how much insulin you need for different situations and combinations of food, activity level and stress level, that's really all you need to know to carry on and keep yourself in good health. Whether or not you produce your own insulin factors into that, of course, and may help you understand why some situations play out the way they do, but on a practical level you just need to be able to work out how to get the results you want on your meter, one way or the other.
Finally, as to your question about testing. How often you test depends on a few different factors. When you're on insulin, you need to test at a VERY minimum 4-5 times per day. On waking/before breakfast (if there's a large gap between the two that can be two different tests), before every meal, and before bed. In the UK, you also legally are required to test before driving and every 2 hours that you have been operating a vehicle (whether it's several short trips like running errands, or one long one). You also technically should test whenever you feel you might be having a low blood sugar, and if it is low you should test again 15 minutes after treating the low.
Incidentally these minimum testing requirements, especially the legally required tests, can sometimes help you make the case for getting enough test strips prescribed, if your GP clinic is trying to cut corners in that department.
Most of us like to test more than the minimum, sometimes a good bit more. For example, it can be useful to test 1-2 hours after a meal, to check whether you gauged it right and see whether you could improve on your judgment of similar situations in the future. You also may sometimes (every 3-4 weeks maybe) wish to do what's called a basal test, to check whether your Humalin dose is adjusted correctly for your current needs, and that involves a good 2-3 more tests. Some (lucky!) people have access to what's called continuous glucose monitoring or CGM, where a sensor under the skin reads their BG levels every 5 minutes or so and constantly tells them how they're doing. Those are the absolute ideal for BG information (and at the end of the day I think we'd all like to be constantly informed about what our BGs are doing, unless you have a lot of anxiety over it) but they're very expensive and still not perfect in what they do.
On the whole I think most people who would say that they "test frequently" test somewhere between 4 and 8 times a day. Some people need to test more often, if they have frequent lows for example, have lost their hypo symptoms, are ill or going through a stressful period, are having a hard time getting their BGs in order, or are on an insulin pump. Some people test less for reasons like test anxiety or due to restrictions on how many test strips they can get. It's all pretty variable and pretty personal, really! The main thing is to test enough to ensure that you are safe (with regards to highs and lows), able to make informed choices about insulin and food, and meeting legal requirements for driving (and work, depending on your work). While not testing so much as to be making yourself overly anxious or depressed/discouraged over your results or to be wasting test strips on tests that aren't going to provide you with useful information.
Hope that helps! Feel free to ask for clarification or any other questions you might have, we're always happy to answer people's questions; it's what we're here for!