Dad with NSC Lung Cancer is Smoking and Drinking during Keytruda. What to expect?

Hi, cross-posting from r/lungcancer. I (25F) am super desperate and dont wholly trust that his doctors are understanding the extent of my dads “lifestyle choices” because he tends to lie. My dad (63M) was dx with stage 4 NSCLC in Sept after having a seizure. At the time, they found a large mass in the upper right lung (although his oxygen is fine) 3 brain tumors and scattered lesions, as well as activity in lymph nodes and a small area lit up on his colon. They radiated two of the tumors (now benign) and started him on Keytruda. He just finished his third treatment a few days ago. However, he was hospitalized for five seizures last night. If my sister didnt randomly decide to stop by right when it started I dont know what would have happened.

So far it looks like there at least 2 new tumors in his brain and the lung mass has not shrunk. Unfortunately, the doctors never followed up with us on his comparison scan between september and november because he was not persistent in asking for the results.

I need advice because i dont think he is taking it seriously. He still chainsmokes 2-2 1/2 packs of Marlboro Lights and drinks about 5-6 Coors lights a day. He is also down to 80 lbs, musters half a meal on a good day, and insists on continuing to live alone. This is probably because he had intense colitis after his second treatment, and just weaned down off steroids for for it last week. I am questioning if ANY of this is adversely effecting his treatment and the tumor growth aside from lowering the effectiveness of Keppra (antiseizure medicine). Since the dx, He has been fully cognizant and “himself” behavior-wise, just drowsy and uncoordinated(forgetting his cane is a big issue) so he + my family thinks he is fine. I dont think he will stop drinking or smoking—because he is an addict—but i just would like to know how seriously this is effecting him and his treatment. I also would like to know more explicitly what we can expect with his progression. He doesnt want to know, so doctors have not told me. I need to have concrete reasons to convince him it is time for a caretaker (if necessary).

Sorry my question is all over the place, im just at a loss. I guess any input is helpful. I want so badly to be able to relate to someone or have advice, but it has been impossible because people usually stop smoking and drinking after Dx.

TLDR; Dads stage IV NSCLC is progressing, wondering if his alcoholism + continued chain smoking + steroids might be catalyzing it and any other general advice on what to expect because he will not stop.