What if, instead of stabbing Dipper with forks and traumatizing him for life, Bill had invested in him as a long-term pawn?
Acted friendly. Offered to help him uncover the secrets of Gravity Falls. Told him how smart he was. Groomed him carefully to trust him, eventually even to the point of letting him into his mind.
Then when Ford comes out of the portal and says “Do you recognize this symbol?”, Dipper’s like, “Yeah, that’s my best friend.”
Can you imagine the reverberations?