Once the company was spun off they were going to get stock options which were basically going to make them all rich; estimated 6-25 million dollars each.
The lawsuit would have been much more risky with no guarantee at all of even winning the case, letting alone getting a huge settlement.

What would he sue them for exactly? He can't sue them for anything related to the sexual harassment issue, as he has already legally settled that with the $100k settlement. As for the set up, nothing happened that cause him any damages. Meredith attempted to make him look bad and failed. That is hardly grounds for a lawsuit, especially since the company sided with him and fired her.
As for working for the company, he has been there since the beginning. He was there when Garvin opened the company up, so he has a pretty sizeable options package giving him a very massive financial interest in making sure the company does well. That's why the sexual harassment problem was so big, because not only would he lose his job, but he stood to lose a massive amount of money in options if he was pushed out for cause.