The ending doesn't make sense? Spoilers Farseer & Tawny Man

[Chrischa]

He had come too far from the boy who loved her, that sixteen years apart had changed him in many ways and it didn't seem possible that they could come back from that.

No, sorry, I think that's the entire point. He didn't carry on at all. When he gave his pain to Girl-On-a-Dragon, he stopped developing. I think that what we see at the end of Fool's Fate is Fitz at seventeen, with the body and life-experience of a forty year-old.
Fitz was half-forged after that, don't forget. Isn't it brilliantly done that after this event, he never once mentions going back to Molly anymore? I hadn't even noticed until I read the Fool's trilogy.

Going off the theory that you can't appreciate the highlights of your life if you haven't got the darkness to measure it against.

In my opinion; the Fool is the love that twines in and out of Fitz' life, according to Gina the hedge-witch. I found myself mentally shouting at Fitz that he could be so thick-skulled not to grasp that!