Yes, I do MX2. No you should not bother going beyond the 2 unit course if you're going to stick to 2 unit, as anything outside 2 unit won't be assessed in the 2 unit exam.
Dude, calm down, it's okay lol. I have nothing against people doing subjects they love.
Once again I don't really recommend learning 3 Unit if you're going to stick to 2U, as the specifically 3 unit topics (eg Permutations and Combinations) really won't help you that much. If you really love maths that much then drop something to take up 3U, and go along with what the class is doing for Prelims. If you don't want to do that, then you shouldn't bother.