Hi Amy,
several thoughts...
its not easy to go through this, as you know, and everyone - patient and caregivers have ups and downs in how they deal with this.

I'll echo the thought that YOU should quit smoking! Smoking IS addictive and a tough habit to break. Imagine if YOU have a tough time with quitting at age 19, how difficult it must be for your father who has smoked for so much longer. Also statistics do show that it makes a difference on long and how much people smoke.

It is hard to make others change their behavior, but you can work on your OWN habits. You take the lead and your dad or mom may be inspired and follow your lead.

They are the parents and you are a young adult. Families are about taking care when needed. It is a tough time for you, but your dad needs your support now. He has been through a lot - phsyically and mentally. Give him time to heal and try to be supportive, without being argumentive.

Support outside the house may also be a good idea. Do the doctors/hospital have a cancer support group? I found it helpful to see & hear others dealing with cancers. The one I went to was not just for head & neck cancers, but all sorts of cancers, but many of the things people were going through were similar. Also is there a stop smoking program he/you could do.

Many people here have found that antidepressants help with depression or anxiety related to the disease. Mention to the doctors the stress that your father, and the family are going through. Reconsideration of pain management does sound appropriate. Morphine does make many people have the negative side effects - I had strange dreams and never could sleep soundly.

good luck to you and your dad, its good news that the treatment seems to work! Hope the responses to you don't sound too severe - we want to try to help and we do know that this is a good place to vent!
Obviously you are doing this because you love him - let him know that.
Take care,
michelle