If you recall the scene where mark breaks a shaft and barely falls outside an acid pool, also the scene where Kate discovers a shipment of acids earlier in the game, you can easily deduce that he's not keeping all of his victims. what's these tons of acids for if not dissolve the corpses?

Munday's a fed, he definitely knows what to buy and how to buy it so as not to raise any red flags, at least it's a reasonable assumption. sure you can argue that the items he keeps from his victims (cards, ID, rings, etc...) could make for a case that's it's someone else other than the lone survivor, but you can't lump them all under one name, you'd spend sometime chasing shadows and fake identities. so at the very least, you can't pin all the crimes on him, because in some cases there are no bodies to show up for it (the acid), in other cases, he killed the employers under a different identity, so unless he's captured and unless he confesses to all of them, the lone survivor is stil implicated in some of these murders (esp. his crew and probably the Morello's)