Donāt despair, Perryās ENTIRE WORLD has been turned upside down and inside out. You two, and even your household, may be the absolute perfect match, and Perryās current change in attitude is to be more than expected. With the initial change, Perry was most likely really shaken up (confused, afraid, insecure, in shock) initially, and therefore on best behavior.
Now that some time has passed, the totality of his situation is hitting home. I would imagine he is now feeling pretty betrayed and abandoned. His whole life is so different. His change in attitude is probably a combination of anger/frustration at all these unasked for and confusing changes combined with that parro mentality of needing to test everything (mostly your patience, lol). So the fact that he feels ācomfortable enoughā with you to act out is actually a good sign. It shows that he is mentally processing these changes and responding appropriately. What he needs more than ever is for his new person to be patient, consistent, dependable and very much āthereā (with Perry in the moment, not just sharing space as roommates). I imagine you are already quite the expert at this given the love you and your Frey shared.
As far as the dog....remember, even though you know your dog, Perry doesnāt. Even if he has been around ādogsā, they werenāt āthisā dog. And Perry is a prey creature. And he knows that. And he is trying to figure how he fits into everything. Perhaps while he is going through this adjustment period it would be best to ānot encourageā interaction between the two. I would hate for an adversarial relationship to develop if it can be avoided by limiting negative interactions for now.
I would expect Perry to continue to switch āattitudesā frequently. A few blissful days, a few rough ones, as Perry comes to grips with his new life. But as time goes on, I expect you will see less of the bad until they pretty much dwindle out. And every bird has their own timetable regarding this who,e process, just like people. Again, the importance of just ābeing in the momentā with Perry combined with predictability on your part is key.
Good luck,I am sure with Time & Love you two will pill through together!