I had good control for three years and then a long spell in hospital involving hospital food, strong antibiotic drips 3 times per day, heart medication which can raise BG levels and so on and I came out back in diabetic territory. Getting back into my old diet which served me well didn't make a difference and rather than the 4.8s and 5.2s I used to see, I started seeing alarming 10.5s and 11's and 9.9s. Alarming for me because that's what I started with 3 years ago.
I have had to go back to square one and am on a virtually zero carb diet to start with. I get to see the 4.8s and low 5s again so, once I feel more confident, I'll start the long process of introducing some complex carbs like pearl barley - it makes a good rissotto and making paella and curries with it.
Also, watch portion sizes. Some of what you have written about can be more carby than you think if you tuck into a good meal. Live like a monk for a few days and eat fish. See if that drops your BG levels. It usually does. Then you can start to think about making your diet more interesting.