For goodness' sake, he's not a coward. He is scarred. His father treated him like a contagious plague, and his mother can't even protect nor take his side. Did he complain? No. Because it's already instilled to him that it's true. He was dying inside and tried his best to continue leaving, but he was never fine. People, like Taeyang, thought he was. But the guy never got his closure, he just avoided his past. You can never expect a broken person to accept love wholeheartedly. It's not for the faint of heart to love someone so broken. It was still bad to hurt Taeyang, but calling him a coward is rude for someone who survived an abuse by actually running away from it.
You never understood Jihwan's pain and it shows. I could explain it to you but I felt like it would've been apparent within those 22 chapters.

I love them so much, especially my baby taeyang. buttt I just hate how cowardly the uke is I just can’t… how can he leave the seme and ghost him for eight years? that’s cruel, so cruel. I know jiwan has his reasons, but I still can’t accept how he keeps hurting taeyang like that. it makes me so sad… and honestly, I really respect taeyang for having the courage to keep loving jiwan, even when he keeps hurting him??!! cause I can't.. I hate coward people that can't fight for his on happiness.. also… it felt so rushed and unfinished?? like hello, what happened to the tall guy from the early chapters??? brooo… btw.. lastlyyy, I LOVED the duo taeyang moments in the early chapters they were hilarious and sweet as hell. ლ(´ڡ`ლ) done yapping lol ~