As a fellow RH er, I have an intolerance to dairy, it is the lactose, regardless of where the dairy comes from, it is the glucose derived from the lactose that is causing your symptoms. As others have said it is trial and error.
The lactose is so much lower in full fat dairy and I can manage a few teaspoons of Greek yogurt, but that is it! No cheese, milk, and so on.
Because I have always had an intolerance, this doesn't seem to bother me as much.
Getting used to intolerance, particularly dairy, wheat, grains is hard, but having an intolerance to spuds (and chips!) Is a lot worse!
Imagine if I also had an intolerance to gluten?
Do you know what they put in place of the gluten?
Potato starch! (Aaaaaaagggggh!)
You seem to be doing ok, at the moment, despite these little issues, be patient, be kind to yourself, you will get there. I have found that I don't miss the food that is making me ill, you have to keep telling yourself, it is your health, you want to look after, you don't want to be ill, or have those awful symptoms. You want to get your energy levels back, feeling like you did years ago and of course be as healthy as you can be.
It is worth it!
Best wishes