1. No, but have vegetarian family members and am not very carnivorous.
2. The Highlands are improving for veggies, but suspect there isn't much for vegans. In the Islands veggie options are pretty much macaroni cheese, and something else if you are lucky, though again, it's better than it was 5 years ago. I think a lot of places would look a bit blank if you asked about vegan food.
3. I have eaten in vegan restaurants in Glasgow and in England. I think a restaurant might struggle in the highlands if it was purely vegan, though I would certainly try it. But in 5 years time, who knows?