I love this start. Since he's started thinking about inconsistencies he should think of Molly not knowing 9 3/4 and talking about the magical world exactly where he should be. What about having Hagrid not McGonnagal or Flitwick fetch him. Are there muggleborn orientation materials? He seems so isolated from the other students in the books. Was that part of the plan?
Getting out sounds REALLY good. Wonder what he'll find when he goes to Gringots. I was so disappointed in the Goblins culture in the 7th book. But hey in an AU we can explain it any old way we want. Maybe they would help him out if he gives the goblin made articles from his vaults back to them with the proviso of future use to be negotiated if needed with guarantee to return them afterwards.