I'll answer those now, and incorporate them into the sheet when I get home tonight.
1. Waterdeep. This keeps it simple. He leaves for a time, wandering, then always returns home.
2. His father also taught him that your works reflect your soul, and that if one stays in the same place for their whole lives their work would be limited in scope. This instilled the idea in Dom that he needed to travel and gain experience in order to "find his soul", so to speak.
3. Dom fell down a flight of stairs leading into his father's workshop. The fall caused mild brain damage. Nothing terribly serious, but enough to give him the shakes. This is why he needed to learn to wield two handed weapons (he can't properly control 1 handed weapons) and it leads into the next question.
4. Dom's accident left him without the ability to use his hands for fine detail work. The shakes he experiences are bad enough that he can't build things with his hands. Therefore, he was never able to learn the crafting abilities like his father. He did, however, find that without proper use of his hands, he could focus more on his mind and become a specialized psionicist. He learned how to manipulate objects like puppets and rearrange their structures without needing his hands. However, while he could have focused on mechanical knowledge as a child so that he at least had the know-how regardless of his lack of hand usage, he chose instead to focus on languages. The way he saw it was that the inventing would come naturally when he found his soul, but along the way he'd have to be as open to other cultures as possible.
Also, his mother always preferred her little boy to hit the books rather than the workbench. She's a wee bit over protective.