Can a 15x8 offset 0 damage my wheel bearings?

I don't see how a 0 offset could damage the wheel bearings. It is when you start adding wheel spacers between the rim and hub that you start to run into trouble with wheel bearings. Then you start changing the geometry of the rim location, putting excess forces on the wheel bearing.

Well, The stock wheel is thin and the one I have now is very wide, having 2.5 inch of the tire pop out of the fender. Will this be a problem?

Running a lower offset wheel such as +\- 0 offset wouldn't do much besides making your turn radius a little worse and having your tires stick out from under your car making it look a rally car haha but no you shouldn't run into bad ball joints unless you run a wheel spacer, which I don't recommend you doing.

The only problem you would run into is in the suspension, if going over bumps bounce the car's fender on top of the tire. The rim is designed for the wider tire, so the forces of the rim to the hub should be ok. (for lack of terminology)

Thanks for your answers guys. It's really helpful. Follow up question: Doesn't it have the same issue with having spacers? New rim is 15x8.

This is one thing I was trying to get at, wheel spacers add a strain onto the wheel bearings, an actual rim center of gravity is designed into a rim.