This is how I would rewrite the sentences to clarify the meaning:
"I haven't had the time (that would be needed to do that)..."
"We didn't have (any) time to talk then."
"Come home from school" means you returned from studying at school. "Come home from the school" means you simply left the building and came home. The missing article implies the action at the place, same as "go to school", "go to church" and "be in hospital".