Chemotherapy effectiveness and side effects

Hi!
My father(54 years old) has lung cancer in it's metastatic phase and also the liver and sides are affected by it. During the last 3-4 days his cough has become harder and more painful for him and it's difficult for us to see him suffer.
However some days later he should start chemotherapy which I know that can prolong his life even by 10 years, which is better than dying after some months.
Since we live in a small city and mountains are near he often went to do exercise and he didn't even smoke(well, he smoked 2 or 3 cigars a day 7-8 years before and he even works in a bank), so I think that he can live another 8 years or more thanks to the chemotherapy, but will these years be like his last weeks or will be like he is not ill at all? Will his treatment be painful? Will we be able to see him doing exercise in the mountains or will we see him in his bed all the time?

I would appreciate any kind of answer, it will make me have less doubts. Thank you in advance!