I do not fully understand your model, but if I would model a customer (or account) and favourites it would look like this. Then a customer can have a collection of his favorites and per product store extra info. Otherwise you could also solve it with a many to many between Customer and Account.
BTW Why is everything a specialization of image?
You can use a Change List action with the Remove option in a microflow to remove a Product from your Product_Favourites association.
I hope this helps.