NAH.

It is a compatibility issue so you are completely justified to rethink the relationship over it. It has been your dream since childhood and you will end up resenting him, yourself and your relationship if you don't think this over now and not 5 years down the line. Proceeding with this marriage may just mean you never get to realize that dream - is it worth it for you?

He has the right to change his mind but it looks a bit like he has put a threshold on getting a dog (having a house) and maybe hoped you would "grow out of the idea" as you both waited for that threshold to be achieved. That's the only reason I'd consider him the A because it would mean he never really considered getting a dog and just strung you along.