Failing him? Good God. You didn't fail him. If you failed anybody it was yourself, and you've now solved for that and good for you.
He is failing him AND he failed you.
Bring somebody with you when you get your stuff. Go in, get it, get out. No conversations, no dramatic telanovella goodbyes us codies love so much, and no trying to understand how he feels.
Apply what you have learned, get your stuff, don't replicate this mistake, and move on with your life. No looking back.
My two cents. Take what you want and leave the rest.
Cyranoak