What would b classed as terminal colon cancer , ie how many tumors (mets) in the body, how big etc ?

Organ failure: Number and size of lesions does not determine terminal disease. Many colon lesions recurr in mid abdomen as extensive lesions producing bowel obstruction. Others present with multiple peritoneal seeding. When end organ failure develops that can't be relieved by colostomy or liver replaced to produce jaundice that can't be relieved by stent then patient is entering terminal state.

Generally endstage: It does not specify how many tumors. It simply means that the cancer has spread and the patient has no chance of survival... It is all likely a matter of few months or may even be weeks. It depends on the vital organ dysfunction (like liver failure or brain mets). Such patients are not active and most likely in the bed and unable to eat well.