My father has MRSA that was inside his knee from a surgery. I am pregnant and with a 3 yr old. Should we stay away until it is gone?

It's not Ebola. MRSA has been overhyped by the media for decades. You will find in in your environment in almost any location. Shopping carts, door knobs, countertops, your own body are all likely contaminated. It is also relatively easy to treat and cure. There is no reason to treat any known case as if they had a terrible contagious disease. Normal personal hygiene can help avoid infections.
No. Mrsa is present on the skin and in the nose of many people who have no idea they carry it. We are exposed all day long to many bacteria including mrsa. Good hand washing after contact is a great idea for everyone, but you don't need to avoid a person because they developed the infection.
Not necessarily. If there is proven MRSA then if you exercise common sense precautions you shouldn't have to avoid him completely. Wash your hands regularly, more if you are involved in changing any bandages. If you have more concerns then certainly discuss again with your doctor.