Mmmm, I'm glad you mentioned the bit in the IL arc when MakubeX kind of lost it for a second. That was one of the harder hitting moments, I thought, when he realized what had happened and sat there looking absolutely miserable, mumbling about what a terrible person he was. I hadn't thought of it in the context of the relationship between him and Sakura in particular, but... yes, that really was the only time we saw him falter, wasn't it? When he realized his plan hurt her...

Now that the third DVD is out, I've been rewatching the IL arc, and even in those first few episodes where we barely see MakubeX, it hit me that whenever we do, Sakura is right there being all calm and protective. So sweet. I don't know why the age difference doesn't bug me at all with these two, but somehow it just doesn't matter. Maybe because, as you noted, in some ways he's a lot more mature than his biological(?) age would suggest.