Brake Light On problems of the 2008 Buick Enclave

I purchased my vehicle January 2014. Since then I have had major issues with it leaking when it rains,. Water enters the sunroof and drips throughout the vehicles overhead as well as soaks the passenger side carpet. Water drips from the visor, the overhead lights (which could result in an electrical fire) in the front middle and back of the vehicle it seeps through the seat belt height adjusters and the area where the side airbags deploy (which could cause deploy issues). The problem has gotten so bad my vehicle is starting to smell like mold and I am afraid that after a year of this problem mold has grown under the carpet as well as in the overhead foam. My biggest concern is if my child is exposed to this for an extended period of time it will flair up his asthma. A child with asthma is very sensitive to mold and mildew and he is very sensitive as well as has allergies to mold. Additionally, when it rains my exhaust smokes and car putts as if water has gotten into the engine/exhaust, the check engine light has come on several times while traveling and no one can seem to find the issue, the check airbag light came on a couple of months after the purchase, and my steering wheel tightens up when I turn and I have already had that taken care of once. As I was driving home today the emergency brake light came on and dinged all the way home. I believe there are now electrical issues with the vehicle due to the leaks and may cause a malfunction or fire.