There is no way to show him other than through your actions. Talk is secondary to your showing that things have changed. You are asking to give him a guarantee and there are none. He has to trust that things have changed. Without that he will never take a chance. Love is risky and people get hurt. There are no ways to show that change is permanent. Instead try to reassure him and make some solid goals for the future one at a time. He has to want to take a chance.
If this has been helpful press accept