I think you should buy a few air purifiers to place them in each room, it will help you and your son. If you don't know which one to choose I recommand you to use Clair air purifiers these ones
I have one in my bedroom and it's really efficient to catch the dust and particules. Plus, if you wanna buy on this website, the shipping is free and they make discount prices nowadays.
I think the best solution is to rebuild the walls, the roof, the house... if you can.