No, I didn't say he was forced to buy and sell. I believe the undercover to trap Misty story is just CYA talk and he was there because he bought and sold drugs with her.
I don't think LE worries about his reputation right now, but if they had really recruited him in some undercover scheme to trap Misty they should worry about it, IMO. Not only does he risk losing his reputation, he lost custody of his son and for all the practical purposes his son lost his father for as long as he's in jail. Jail time is unpleasant and sometimes potentially dangerous to the inmate's emotional or physical well being. Suppose his psychological health suffers from having to cope with the information about his daughter's death away from his family, in isolation or in the middle of other disturbed inmates. IMO it wouldn't be right for LE to use a missing child's father in such a scheme. If you want to get his ex-wife arrested there are other ways of accomplishing it that don't involve any jail time and loss of reputation for the presumed innocent undercover victim's father. They can get the guilty ones without punishing the innocent ones who just helped to gather evidence inside along with them. It makes no sense to me.
If he's thought to be guilty and LE has reason to want him to land in jail for his own crimes (drug related or otherwise) then it's of course a completely different story.
Anyway, I never really got the impression from RC and TN's comments that this alleged undercover thingy was something that had been agreed about with LE. IMO it was portrayed more like he got the brilliant idea to sell drugs with Misty to get her arrested all by himself, didn't talk it through with anybody except his mom maybe and doesn't care if it gets him personal prison time or not if it works.
Then again... if it doesn't make sense to you either maybe he just sold some drugs?