@Siikalahna
If i'm being honest, it's likely that plunder doesn't actually work like he thinks it does, the name of the curse being "careless retribution" makes me think as soon as he tries to use it, the skill just automatically activates on him and makes him suffer the consequences of using it, remember he can't use it right now, this is also if he can just copy skills or if he actively steals them, if it's a copy then it probably has side effects to use, personally i think he lost the skill but we'll see.
It's also worth remembering that god essentially abandoned that guy there while the mc and the 2 girls he wants to return home if they so wish as they are "good examples of humanity" or something like that.
I'd say the big risk factor here is the king and princess, who i expect to be pretty evil on their own, and probably a bigger threat than the dumbass "hero" wannabe.
That said, one thing that's bothering me is he acted like he heard the 2 girls talking, but he also ignored what they were saying, so either he's bluffing (entirely possible), or he's really that dumb.