Before reading this, is seme a douchebag? Is this worth reading?

Yes he is a douchebag. He's more of the "I don't have an ounce of common sense" kind of douchebag.
Personally I hate power abuse dynamics so I'm going to drop this.
I liked how the uke stranded up for him self at the beginning and thought this would be about how the seme will change, but NOPE the uke ended up caving in after some pressure
So yeah I hate it when they abuse their powers

Exactly what I thought

UGH! Worst kind of douchebag!
I hate them the most and have no tolerance to them (╬￣皿￣)
Thank you for letting me know, won't be wasting my time on something so frustrating like this

douchebag? yes, but he realizes his mistakes and apologizes properly. the mc calls him out on his behavior too (i didn't expect any of that so it was a pleasant surprise)

So he does become a normal, functioning human-being at the end, Tbh that's surprising, and it's kind of a relief that Korean authors stopped normalizing toxic behavior.
I tend to get emotionally invested reading manhwa's, so I try to avoid these types of stories