Hi, welcome to the forum.
For more information on the hba1c test and what your results means, this site provides a good explainer:
Glycosylated haemoglobin & diabetes. HbA1c facts, units, diagnosis, test frequency, limitations, control, conversion. How blood glucose levels link to A1c.
Your result is definitely diabetic, but comes in the "could be a lot better and needs to be reduced, but could be a lot worse" category in my opinion. Mine was 83 at diagnosis and I've seen accounts of people's being well over 100.
Beyond that, I don't have experience with your specific conditions beyond diabetes, so I'll leave the advice to others around here.
In terms of diabetes, it's possible your previous test results may have been overlooked or misinterpreted, many around here have experienced this. Are you UK based? If so, do you have access to your medical history on the NHS app? This will allow you to look back over every test result you've ever had and will let you see if anything has been missed/overlooked.
You mention dry mouth, however as for whether you should/could have noticed (which I think is what you were implying), maybe, but it's easy to miss and many symptoms are non-specific. Diabetes symptoms can be quite subtle, as yours were, right up until they're not. With the benefit of post-diagnosis hindsight, I had
some symptoms for probably 1-2 years. Did I put these down to diabetes? No. Should I have done? Maybe, but they were quite subtle, happened in isolation, and were disconnected from each other over that timeline. It was only in the last 6-8 weeks prior to diagnosis that I had several symptoms hit, all in quick succession, and other explanations become quickly and increasingly improbable. Not everyone gets this path of symptoms though. In short, I wouldn't let it play on your mind. Assuming you're not a doctor yourself, there's little to nothing you personally could have done to spot it earlier.