My husband also has stage 4 with metastasis to liver. Really sucks.

I don't know who your oncologist is associated with but have you asked for a consultation with a dietician? They should be able to help figure out ways to avoid malnourished and maintain weight even if he has difficulty with solid food. Hey may also be able to identify potential issues. For xample, is tomato soup acidic enough that it is an issue?

In my husband's case a dietitian stopped by once while he was doing chemo. She had a couple of handouts, ran down a list of suggestions (a couple of which sounded good to him) and had a few useful tips. It might be worth a. shot.