Poor guy. Wanted a last pop before popping off.
My perception was that Lane was a partner, but wasn't financially compensated to the same degree as the flashier partners. He said this episode that he had been "operating at a loss the last three years." Maybe school + taxes + wife's expenses? I think that's part of his big emotional response to the bonuses; yes, he needed the money to pay back his embezzlement, but he also just felt like he deserved one after getting shat on since the new firm opened.
My sense is the show was trying to indicate he was living above his means but probably failed to convey it in a full way.