Comic book writers say that kids don't want their heroes happy and settled. (Sound familiar?). But I don't see that being true. They may not want to see adults kissing, but that doesn't mean they want them miserable.

Indeed. I think kids have a decent idea of how relationships are supposed to be, and that you can't just retcon yourself back to square one. Kids are much smarter than we grownups give them credit for.

ETA: I just asked my son if he wanted to watch POTD and he responded "no, thank you." So, I asked why and got the shrug. But when I asked if he thought that the show was too sad now, he answered with a sad little, "yeah." Put that in your pipe and smoke it, RTD.

Case in point. I think your son understands that this isn't how the Doctor is supposed to be, and it's rather ruined his enjoyment of the show. Smart kid.

PS: happy birthday! :)