Valygar, Keldorn, and Minsc will break away from the party to kill Edwin if he is present
That's false. I just now got done playing through Baldur's Gate 2: Shadows of Amn with the party consisting of me, aerie, valygar, minsc, edwin, and yoshimo (later replaced by imoen). all you have to do to get them to stop bickering is get the nether scr(WARNING:SPOILER!!!)...oll for edwin and when he finally says he can decipher it to become a lich, except not undead and much more powerful, tell him to do it and he'll turn into a chick. after awhile (filled with your party making respectable remarks, i think my most favorite was when minsc randomly said that boo was saying that he (boo) was wondering where edwin has gone and why theres a girl in his robes. or the one where just after he goes chick you can say "...oh, and nice rack." edwin actually agrees to this!) a red wizard (which is what edwin is supossively affiliated with) will show up and ask where edwin is. you say he isn't there. the red wizard leaves, then shows up again some time later and points towards edwin(a) and says its him and undos the curse. then edwin attacks him, and so on.
after all of this has taken place, the entire party will stop bickering at him except for the occasional valygar + edwin debate over edwin speaking, however they will never actually fight and minsc and edwin will never talk again. i've never had anomen in my party even when playing a female character just for the fact that he is a complete idiot about the ideas of neutralism and then (from what i've read) he turns neutral later on if certain conditions are met. complete haughty retardism and i'd kill him if it didn't mean that the whole copper coronet would start attacking me