At some point we need to accept he's just a normal character that needs a rewrite to his route.
What kind of rewrite? I personally enjoy the "normal guy" Dean. His Story feels like a vacation compared to most character with their (family) issues. The main flaw of his Story is the missing bridge/logic between his character-flaw "Abadonning Rami" to his "dating" problems and other parts of his bahaviour.
But I can see him breaking under the threat of death and abandoning the group.
He already abandoned Rami. So Dean coming to the rescue of Dave or Hoss or even Tyson would be a nice end of his Story-arc, no matter if he is on Memphis Payrole or not. I think Dean is pretty brave.
a) Dean volunterd (it's only brave if he does not work for Memphis) b) Dean tried to stop Sal from killing Roswell, but gets himself killed c) On Benson death, Dean and Tyson are the first to spring into action. d) He took a hit from Sal without resisting/dodging.