My dad has swelling belly from liver tumor how long does he have?

Probably not long: Swelling of the abdomen from a liver tumor is usually from very advanced disease. The primary causes are either massive growth of the liver or fluid in the abdomen caused by blockage of blood flow through the liver because of tumor growth. Chemotherapy or radiotherapy is not likely to have much effect at such an advanced stage. Death within weeks to months would be the usual outcome.