You need to look at Total Carbs, not just the sugar, as all carbs will raise your blood sugar.
3g per 100g seems a bit over strict, you’ll find it very hard to find foods which fall into that category! The suggestion of 10g per 100 is more realistic. It sounds like you have made a good start by halving your carbs in the evening, if that goes well try dropping it further or substituting the carbs for something else, more meat or veg, or you can make cauliflower rice or courgette spaghetti for example. Berries and yogurt is good for breakfast (best if it’s natural yogurt as the flavoured ones contain sugar). As far as fruits go, berries have the least amount of carbs, apples/oranges/pears are in the middle and the ones with most sugar are the tropical ones such as bananas, pineapple, mango etc, which are probably best avoided. And grapes/raisins are little sugar bombs!
If you can get hold of a blood testing meter then a good plan is to test just before you eat and again 2 hours later and you are aiming for a rise of no more than 2-3 mmol/l, any more than that would suggest that something in that meal doesn’t suit you. The doctor may well say that this is unnecessary, however if you really want to know what’s going on and whether your diet is helping you, it’s the only way to find out. The cheapest ones are Gluco Navii and TEE2 I think (it’s the ongoing cost of strips that you have to think about if you have to buy your own). And whatever you do with your diet, you have to find a way that you can stick to forever, if you try to cut everything down too drastically you’ll probably fail. One step at a time!