Would $1500 dollars be enough for 1 week in Montreal?

Why ANYBODY would set foot in Montreal is beyond me. Unless they wish to become dinner for the local Haitian and Afghan barbarians.

with an Airbnb it could be possible, will cost you around 1000 to eat, stay and transport and around 500 for fun

Maybe. A hotel would take most of that, and food would get the rest. You would not have much for having any fun.

That depends, does that include a hotel room for six nights, and your transport to and from Montreal ? If those things have to come out of the $1,500, then you will have very little left for food, never mind any fun things.

That depends on where you stay, when you go, and what you plan on doing.

But it's definitely possible as long as you don't go during the peak tourist periods and insist on staying in 4+ star hotels

Depends where you stay and eat and what you propose to do. I stay in college residence and buy food in supermarkets. That would come in about $100 per day, with some night life.

i dont see why not

It might be enough to cover seven days in a hotel if you shop around.