I think Dr. Galland uses Rifaximin. But, as you say, you'll know a lot more after the HBT. No sense jumping ahead.
I know how you feel, about the confusion, that is. Both the Pharmaceuticals and the Supplement industry have really capitalized on this Syndrome and the multitude of Symptoms and Disorders that surround it, and I think it's in their best interest to keep it that way: confusing.
But trust that you are in good hands with Dr. Galland. He's one of the MD's who really understands this stuff.
About the carbs, any confusion about that can be settled by using the glycemic index. Just google the food item with glycemic after it, and you can find out what it's value is.
Most of your carbs should come from green veggies. Very few grains, no wheat, and if you do eat/tolerate grains, eat them in small amounts, and only in the evening. That way they don't cause cravings throughout the day.
Don't eat anything over 55 on the GI. Lower is better.
You may have to adapt your diet, as well as your understanding as you go along. But hang in there, keep learning, and you will come out of this just fine.