Does "I’ll be bound" mean "I'm sure"?

[NewHopeR]

And "assessment" here refers to "an amount determined as payable"?
Plus, should "ought to paid" be "ought to have paid"? Such grammatical error is acceptable in conversations?

Context:

　“But, Will, I can’t understand. What do you mean?”
　“Miss Scarlett, I sure hate to bother you with more trouble when you’ve had your share but I’ve
got to tell you. They say you ought to paid lots more taxes than you did. They’re runnin’ the
assessment up on Tara sky high—higher than any in the County, I’ll be bound.”

 

[Tdol]

Such grammatical error is acceptable in conversations?

Conversations are often littered with things that would be considered errors in writing.