You flatter me, Plaw.
(BTW, where's your input in the quotation game???)
The description of their relationship with Lucy is in chapter 22, it never says something like that exactly, just that it was a "lusty passion for each other."
Book never says too that she was not good looking. In the end there's a passage in which Fontane sort of admires her looks.
And there's one more mention about the comedy he was playing - when they meet with the Don before meeting Solozzo. Tom looks at his sleepless appearance and thinks "He must be humping that maid of honor still."