I didn't say anything before, because I didn't want to add to your worries, but bad side effects are a good thing. When cancer therapy goes easily, it often means it's not working. The crappier he feels, the more the treatment is working.
It sucks, but it's a good thing.
John learned this when he was studying up on chemotherapy and when he was studying up on cancer therapies. He was middle-of-the-road side-effecting. It was bad, but he also studied enough to know he was given a break on how bad bad can get. He "only" got up to shivering uncontrollable for days on end, and knowing wayyyy too much about what was coming out "the other end" compared to what he ate, when he could eat. (Only person I know who can tell the difference between root beer, peppermint, wintergreen, and licorice hard candies based on what comes out the other end. lol) And he had all the way up to little-vomiting, (versus projectile vomiting.) But as hard as it was to be there for him while he went through all that, the chemo was working.
He was one of the first people ever to get the word "cured" for Hep C. (If anything, before that, people were told, "in remission.") And he was one of the first people to get the word "cured" for the cancer on his kidney. AND he got that word through another word you just learned -- "cryoablation."
Now, kidney cancer and stomach cancer are two different kinds of cancer, so I still can't tell if this will work out for your dad, but this I know. I am happier to hear he doesn't feel well, than I would have been if he did feel well.
And, something else that I appreciate knowing because I do keep a mental scrapbook on what the Lord has done for/to us over the years. The Lord can fix anything before it even happens. He can fix stuff moments after it happens. But we are the 11:59:59 people. (John and I are.) For us, the Lord tends to fix stuff at the last possible moment when there is nothing else that can be done, and no other schemes and plans we can come up with. He waits for 11:59:59, when midnight is the deadline. BUT he does give us what we need then.
So, just because this is the last thing your dad can try, does not mean it will fail. My experience is God stretches us more and more to give us that patience thingy and that perseverance thingy whether we want it or not! (And, I never want it until it's over. lol)
Do not give up. The Lord does this to his kids often, and it still comes down to two lessons he wants us to get:
1. I love you more than you will ever know.
2. Trust me.
That's it. Every lesson the Lord gives to us is one of those two lessons. The huge lessons are both of them.
This is working out exactly like the Lord planned it, exactly for your good, your dad's good, your family's good, and always to God's glory!