Im with you in that not all people who committ suicide are cowardly or are bad people. Junior Seau comes to mind. However, I dont think you should be trying to make that argument in this particular case. This POS's suicide was clearly a cowardly act. He took the easy way out after he made a poor split second choice in the heat of an argument.
I agree that it seems this guy lost control of the moment and killed her and knew he was headed to the pen, couldn't deal with that lifestyle.
As for junior, i read where a lot of his woes were financial. He owed millions to the vegas casinos. That botched suicide attempt when he drove off a cliff was on his sons birthday. Pretty crappy move by a father.