Betta Fish: Do I need to euthanize Clank?

Clank. First 4 photos are Clank. 4th photo is Clank in his prime. Last photos are of his beautiful children. (In case he needs to be commemorated in this post) I have raised his kids and sold them to well vetted ethical homes. Clank in his prime was a sight to behold. He lived in a planted 30 gallon but has since moved to his own 10 when he started getting limited mobility. He was one of my first fish getting back into the hobby, now I’m raising zebra plecos and have two rooms of tanks. I loved him so much he got me back into breeding aquarium fish. It was so cool to see what a great father he was to his fry. His mobility issues are nothing like the swim bladder that I have treated.. I love this fish but I’m starting to question the quality of life he has. He’s been deteriorating. I have tried many solutions and medications. He gets a 50% water change daily I’ve given up on meds after a few months of trying different things. I’m starting to believe he’s just old and sick. He sits in the same spot all day every day and it’s been this way for 5 months with no change. He still eats, he gets brine shrimp and gets up to eat. I can tell it’s hard for him to get to the surface for air when he needs to and today I noticed he’s breathing heavy. He’s always lived alone with shrimp so there’s no possibility he’s caught anything from my other fish I don’t cross contaminate cleaning supplies since I keep such expensive fish. He has a small tumor on his back and his right eye seems to be enlarged. Possibly Popeye but I’ve already tried kanaplex. What do I do? I have clove oil if the best option is to euthanize. I don’t really want to see him suffer. Every day I kinda expect him to have passed when I turn the lights on but he’s still kicking. I wish he would get better. He’s well within his years though so this might be as good as it gets for him.