Thank heavens for your comment
Now I know not to read any further to not get triggered
It's interesting how many ppl read the whole thing and saw how many severe hardship Doram suffered and can not understand why he feels resentful and angry.
Actually I don't think Doram knows that his house was proclaimed as traitors as emperor punishment onto the prince
I'd go even further to say: little child opens up to a stranger to the point of welcoming him to a family ritual and is promised protection and help. Then his whole life being thrown into hell, for no reason or fault, and the promised help never received. Everyone he loved died and disgraced
Yeah, it's not fair, but pretty much anyone would feel that way
Plus now Doram has his current and past memories: so this man or god whtvr didn't come to his rescue when most needed, but later had a gall to force him into marriage and expected affection
So figure why would he be mad...

It’s painful I know! But you gotta understand "the resentment" is from when he was the child and towards "the god". Because the God is prince himself, who also promised him to protect but neither forms (human or god) were there to protect him when he was literally in utter despair of loss and sorrow.
So, do the math or re-read the chapters, yeah?