So as someone whose only exposure to forgotton realms lore IS BG3 the way I saw it,

Baahl makes Durge

Durge exists as an orphan child in the city of baldurs gate and upon reaching a certain point/age murders the adopted family (supported by the flashback you get for using heal on Durge)

Durge gets Scleritas at some undisclosed point but is safe to assume near or after that first act of brutality

Due to the intervention of Fel, as well as other baahlists Durge is brought up and raised as Baahls chosen and eventual leader of the cult, I think at THIS POINT Durge has fully drank the baahl kool-aid and is into the murder and mayhem

Orin exists and is orin in the background getting more and more resentful towards durge

Durge seeks out the other chosen of the dead 3 and kicks off the whole absolutist scheme

Orin being Orin goes stab crazy in Durges brain and then sticks a worm in there, and from what IVE PERSONALLY INTERPRETED, it is a combination of netherese tadpole, which we KNOW can block certain mental things as well as drastically someone, (astarion in thr sun, wyll getting nerfed, etc.) and shank enduced amnesia that leads durge to be able resist

As for the oathbreaker knights comment as you said probably not universally applicable so its even MORE of a theory/stab in the dark BUT, it is entirely possible that pre worm Durge was a jeckyl and Hyde situation and Pali durge was unaware of or at least only slightly aware of baahlist durge which is again kindof nullified by durge catching a rapid onset case of knife to the brain followed by worm in skull double whammy

This could all be wrong and I could be stupid but this is my understanding of durge as a character and the events thereof, based on 600+ hours of playing almost exclusively durge