Aquariums: How do I know when its time

My boy with a Tumor. (I thought was constipation) Ive done everything possible. Hes had many salt baths, fasting, daphnia, parasitic treatments, internal and external.

Turns out im pretty sure its a Tumor. His belly is lopsided and droopy on one side. (You can kind of see it in the photos). His scales are starting to spread down by his belly.

Hes still eating and behaving normally. When I saw his scales start to spread (not pineconing just from the swelling in his belly) my heart sank as I know im going to have to call it soon.

Im wondering when, if he stops eating or starts acting differently, im calling it then and putting him to rest.