If he can make a vow to discontinue socializing with his friend, then in turn give him the benefit of the doubt and allow him to prove himself to you.
If he has never given you a reason to not trust him, I agree give him the benefit of the doubt.
When someone gets into these behaviors, they cannot think rationally, especially with alcohol. That is why he was so emotional the next morning because he remembered parts of what happened or sees a bruise.
Unfortunately, addictive behaviors limit the rational thinking and abuse occurs. Loss of Control:
(hence, throwing wedding ring out the window)
In this state the person experiences a sense of loss of control. All attempts at stopping the acting out behavior, regardless of commitments, fail, and it literally feels as if something else is in control. Negative Consequences:
Soon after a person experiences loss of control, it is common for negative consequences to begin to unfold. The weight of the addiction begins to wear one down. It requires tremendous energy to live this double life. It is common for an addict to live in constant fear of being found out or caught. For many, it is a spouse that will find evidence of the addiction and begin the confrontation. It is also common for those who are confronted with indisputable evidence to minimize it and swear that it will never happen again. But a person in this phase can no longer ignore the reality of negative consequences that are following their addictive behaviors.
It sounds like he is willing to get help and listen to you. This is a wonderful thing. You can read many posts on this forum where the husband won't even listen to the spouse.