Your character has displayed superior melee abilities, and superior magic and basically superior everything, even when it wasn't listed in your bio. You have also added abilities that were not listed in the bio. At the moment you have made your character into the most powerful in the RP who, given what you say he can do, shouldn't have struggled with anything even slightly.
He should not be better at melee then two people who can pretty much only do melee, one of whom is King Arthur.
Also, "wanton urge to murder random party members"? Let's see... dislike and suspicion directed towards some of the more evil-seeming ones... and in one case where the character's actions threatened to kill everyone involved, Archer actually killed him. Your character has repeatedly done things that make hims seem ridiculously suspicious and callous, and then outright says he kills people to live with no effort to point out that it's only his enemies, even if that's a lie it's far more intelligent then saying he's a murderer in front of people he has no idea how they will react.
In fact, why would they treat him different because he's a "party member"? Any character who brags about murder and does all the crap Sorin has done would be subjected to attempts to kill them.
Why should we completely violate our characters' concepts to bend over backwards so you can keep in a line of dialogue? We shouldn't have to.
It's even worse for Archer, who is extremely dedicated to the "kill one to save a hundred" ideal and that sort of thing basically forms a huge amount of his character.