So I shot Felix in Ep1 thinking he was heartlessly backstabbing his own adoptive children. I figured it didn't matter because he killed himself by opening the briefcase (an oddly amateur move given his experience). It did sting a bit when he called Fiona his favorite in his last moments. I felt confusion and regret build after that as I found out all the care and effort he had gone to in the care package he left behind at the hideout.
When I found Felix was an option for the endgame team I googled a lets play and discovered how messed up what actually happened was.
So apparently Felix took the money out of the briefcase, replaced it with fake cash, stashed the real cash in the furniture in the back of the vehicle, rearmed the bomb, and then killed himself while praising his adoptive daughter. His plan was always to commit suicide to make it look like the cash was destroyed to protect his children from Vallory's vengeance, and he stuck to that plan with his dying breath even if Fiona mortally wounded him.
Only the way things ended up the money was all lost in the desert during the monster attack, Vallory found an excuse to hunt the group anyway, and Felix died with his daughters hating him and never to know the truth. He gave up everything and it all turned out to be a pointless waste.
I really wasn't expecting such heavy emotional weight to be hidden in a side option like this. I kind of wish Fiona and Sasha at least found out the truth in the scenario in which he dies. As is this is one of the sadder moments I've come across in a TT game, though the real impact of killing Felix is only to be discovered if he lives so I guess most players who killed Felix or let him die don't even find out that it was all an act and completely selfless.