how much weight does this bag can hold?

I put about 75 lbs into the 40 inch Bag on a regular basis. It handles that weight just fine.

Can a 32" flatscreen tv fit in it?

With dimensions 40.00" x 17.00" x 16.00", the 40" is measured from side pocket to side pocket. So putting a 32" flat screen would not be advisable.

How durable is the bottom surface? I've had a similar bag crack on me from throwing around.

The bottom and frame are durable. I bought two of the Rockland 22" bags to haul our segway minipro's. Each weighs in at slightly under 30 pounds. We need the bags or our segways when we travel: train, auto, ship. The bags have held up without a hiccup. I bought several other bags for our before the Roclands. All failed. The wheels on the previous two bags collapsed within 100 feet from our car on our way to the train station. I could not recommend these bags more highly.