[@Holy Soldier]
Is the character supposed to specifically represent his sin in his personality overtly and distinctly? I kind of sort of assumed that since we've don't really have our memories we can be the sort of people society molded us into after we've regained our bearings as opposed to the people that we were when we got cursed - that is, until our past catches up to us. 

As of now, as i see it, this guy's lust is expressed in the fact that despite all things said and done he is supremely self-centered  and almost incapable of commiting to anything except something that he himself wants, narcissistic to the extreme, even if in a sort of passive, internalized way. His ability's nature especially helps him to extend almost no effort towards dealing with the outside world as opposed to working towards his own desires - but at the same time, torturously, he can't just materialize his own wishes in a way that he can do with the wishes of others.

And nah, he isn't specifically modeled after Beelzebub, nor as a demon nor as a philistine god. The festering fly-shaped mark symbolizes the infectiousness and the insidious nature of sin overall and lust specifically as the most carnal and visceral sins - closest to the flesh, pestilent and incredibly hard to scrub out. A fly in christianity is a symbol of sin and decay, both physical and spiritual, even in detachment from Beelzebub specifically. Especially considering that "lord of the flies" is just one of his interpretations, other being "lord of those who dwell in heaven/lord of the heavenly/lord of those who fly" from Baal Zəbûl as opposed to Zebub, both originating not in the christian writings but among israelites and philistines.