Am so sorry to read this op, but the good news is they're found it and know what's what. This is the most important thing.
My best advice and what got me through my own cancer diagnosis was to stay away from here and other online message boards. Your husband's cancer is unique to him, so what everyone else has to say is immaterial, even if their cancer looks the same on paper. At this point in time, listen to your husband's MDT. His cancer nurse will be invaluable. If you must talk to others online, I know there's a support thread on here for partners of those with cancer.
When I was going through cancer, I went to a Macmillan drop-in centre (as there was one at my hospital). Had there not have been, I would have called them. I went to Maggie's too I preferred Macmillan. They were amazing, I cannot recommend them enough. They have various information available too which looks at all aspects of cancer, treatment, and living with cancer, both as someone with it, and as the partner of someone with it.
What I do know is treatment for lung cancer has come on a long way. Yes, it's a hard one to deal with, particularly if it has metastasized, but, they are ways of treating it palliatively which can extend life. However, treatment is hard, even when one is in the best of health, so you need to consider the cost of it. But, that's getting ahead of things, not least because his oncologist might know of a medical trial and all sorts of things that could help. For now, get all the information from his MDT and then consider your choices. If you want a second opinion, ask to be referred.
Wishing you and your husband well 💐