I'm sorry to hear about your dad's cancer. This is a frightening situation for you and your reaction is normal. 7 centimeters is a fairly big tumor. There are a lot of treatments for lung cancer, many of them new in the last couple of years, and new ones are being tested and approved often. You'll probably hear from people who have been in similar situations, who were diagnosed after some sudden alarming symptoms.
If you want to learn more about lung cancer, a good place to start is Lung Cancer 101 on the Lungevity main site. if you haven't been there yet, the link is https://lungevity.org/for-patients-caregivers/lung-cancer-101. When looking for online information about cancer, be careful about your sources, since not all of them are reliable. Also, don't get hung up on survival statistices. Most of them are based on 5 year survival. With all the new treatments, the stats on lung cancer are out of date by the time they're published. These forums are a good place to find information, hope and support. Let us know what questions you have and how we can support you. That's what we're here for.