HI Tal, Sorry to see your frustration--but hang in there! Remember this journey will often take a few steps forward and a step backwards!! Give your H some time-perhaps he has to figure out why the PO Box is important to him and he wants to think before discussing in haste. I've been speaking to myself often "choose your battles" "how important is this?" and perhaps your H is going through this in his head before discussing it with you.
Based on all the great progress you two have made, I'm sure he'll realize why this is a big deal to you and you will both be able to discuss it and come to a solution together. PATIENCE is key. It is ok to get frustrated and it sounds like you calmly let H know that it is a bothersome area for you--he's not running/storming away--so remember to look at the nonverbals again--maybe you're not hearing what you want to hear--but perhaps he is speaking to you differently!!!