The Great Gatsby, he had never seemed capable of such a statement

I'd like to know if in this extract from the chapter Seven of The Great Gatsby the adverb "faintly" modifies the verb "seemed" or rather the adjective "capable" and which sense he has.

“I’ve got my wife locked in up there,” explained Wilson calmly. “She’s going to stay there till the day after tomorrow and then we’re going to move away.”

Michaelis was astonished; they had been neighbors for four years and Wilson had never seemed faintly capable of such a statement