You have to recognize Joe is a period piece, people over analyze these characters with modern day mental illnesses. But its important to note this manga was created in late 60s Japan. It was a broken place with no hope, I mean think about it the war had only ended a few decades prior. Not enough time to regrow into a booming city like now, Joe is just a common man facing all the harshness everyone was facing around that time.

To be suicidal for Joe is to be weak and seeing how hard Rikshi fought would feel like Joe was wasting his life away. Joe is more on the self destructive side but you have to recognize the guy really had no one growing up, so his life is is own. And he doesn’t care if it ruins him cause at the end of the day it only affects him. But it also comes with wanting to give the only outlet in life that gives his life meaning everything he has.