At this stage it can be really hard to tell, for anyone. The illness makes you feel like you can barely get out of bed. Depression makes you feel that way too. Add them together and ... you don't want to get out of bed. Add to that a person who prefers to have people cater to his needs, and is maybe facing the first really big scare of his whole life ... that's a lot to untangle. That scan could come back perfectly clear (which would be great!) and he'd still be a sick man. How much he did to himself is moot at this point (from a health perspective, not a mental one). He has to heal, and it will take longer now. But (as you and your daughter know) he's got to do a lot of it himself. Just like you can't lift weights to build someone else's muscles for them, you can't do his swallow exercises either. Nor can you eat the calories, etc.

This is a totally long-shot idea, but since so much of what you describe of his issues is mental ... is it even possible to have him temporarily committed for his own safety? Preferably at the same hospital that deals with his cancer treatments? It might be a good wake-up call. Not the sort of thing I'd normally suggest, but if they can help him get a grip on his depression, and his new health reality, in a setting that can handle his physical needs better than you can ... it might be the eye-opener that he needs. They can do things like that for 24 or 48 hours. (We had a relative who made some very concerning statements once, and he lived out of state, so we had to call for a welfare check. It wasn't pleasant for anyone, but it was a bit of a wake-up for him to at least think about his intentions and his statements ... it hasn't happened again, thankfully.)

I know it's a weird idea, but it may be time for out of the box thinking?