Yes, I would say it may be strong enough but I would still mount it to the shelf from underneath or on each side. It is sturdy though and I love the cabinets. Remember, these are all made from particle board with a formica type coating.....but they are good quality.
I'm sure it depends on how well it is mounted to the wall, I have it lag bolted to my wall, a block wall. We have plates and pots and pans in itand two crock pots on top of it so that is approximately 50 pounds and it is holding that weight with no issues
Yes, but not easy. The cabinets are covered in a laminate. You will need special prep and special paint. It will be like painting a kitchen cabinet. Paint stores and big box stores sell paint kits for painting cabinets.