well tbh i wouldn't know much about how to import box2d into an existing project lol, but you could always just convert your project to a phaser type thing phaser.io
then with 1/2 command, all your objects are physical objects that interact with everything else :P
I could just replace the rects with some kind of box2d property (a body or whatever) and use that to render my stuff, while still updating the physics world.