Keep in mind that just because he is grumbling and acting po'd doesn't mean you have to get upset about it! I mean, the fact that he is acting that way says a lot about him, and the fact that you are moving on calmly and with dignity says a lot about you!
Also, why are you thinking of it as him "letting" you have it? Instead of asking permission ("H, is it ok if i take this?" ), maybe play around with some more assertive phrases (not spiteful or aggressive, just asserting yourself. Is there someone you can role play with? Maybe you got upset because you asked his permission...and he gave in hesitantly (which is not what you were hoping for). If you don't look for permission, but just express your wants, then it won't be upsetting when he doesn't give his permission!
I've found it helpful to say in my head whatever I would like to say out loud-- and keep a calm smile on my face. Sometimes I hum a sweet song but the lyrics in my head match what I wish I could say to him out loud. I can picture you doing that as you pack! Do you have an anthem or a mantra? That helps me too during difficult moments.
