What’s our puppy?

Hi All,

New here and wondering if our adorable pup is what the possibly shady breeder/pet shop claimed he is which is a 3/4 pug, 1/4 Boston terrier. I have seen his alleged lol Dad in the pet shop in the past and he is a fairly stocky pug x Boston who has an Aussie/English bulldog look but is still smallish and Mum is a pure pug. We have had him for 5 wks, getting him at 3 months old, now 4 months. 4 wks ago he was 5.6kg now he is 7.6kg. In the puppy weight calculators, we get estimated adult weight as approx 23kg... this is definitely bigger than any 3/4 pug alive...
The breeder works at the pet shop, is brother of pet shop owner and father of staff member who sold pup to us but despite being advertised at pet shop and purchased there, the pet shop owner says he hasn’t actually sold him (cue dodgy music of some sort lol) and father is that afermentioned dog “as far as he knows...”.
I’ve looked up the breeder and noted he has Am staff looking dogs online. I’m wondering (as did the vet) if the bigger am staff got to pug mama around the same time as the planned breed btwn her and bugg since a litter can actually have multiple fathers...

We adore this pup and he has a beautiful gentle nature but I am curious to know what I’m in for especially since we live in a rental apt with permission for only small dogs.

Thanks for your thoughts