Hi. I'm so sorry to hear about your dads diagnosis. I don't really think anyone can tell you how much time your dad has, but the doctors might be able to give you a rough idea. My mum also had severe COPD and then lung cancer (I don't know which kind). They saw what looked like a spot on an x-ray in November 2017. She wasn't diagnosed until February 2018 and then passed away in May 2018. She wasn't eligible for any treatments though, due to overall not great physical health.

Maybe things will go well with your dad and he will be able to have treatments to give him more time. 

All the best