Chalk the hair-puppeteering up to that particular human just being weird. Maybe he's got extra nerves in his scalp.

If Astrid knew of Donald's apparent desire to become a hermit, she'd be a very sad fluff. And would also most likely rack her brain in an attempt to figure out a way to convince him to stay... beyond a perceived duty. She likes having him around, as if the snuggling wasn't enough to tell him that.