What do to with the spare Roo?

So, I have 12 week old babies that have been out in the yard now for about 2 weeks. I was supposed to have 2 hens and a roo, but sadly I have a spare roo. The other thing about him...I just don't think he's a very healthy boy.

Having had them since they were 2 days old, he was the runt of them all. Slowest to feather, the only one with crusty bottom, and now his crop is always floppy. It's been this way for weeks, and it doesn't seem to get any better. They all at one point had it when I switched them from chick starter to flock raiser, but after having all the grit they want only his is still weird.

Being a rare breed (pencil laced plymouth rocks), I had initially considered selling him since I thought he might bring a few bucks (I was thinking 20-30 bucks)...but I worry he's just not healthy enough and that he should be culled. He might a make a great stew. Heritage breed stew anyone?

So, I'd love your opinions. He's always been kinda sickly, and I'd feel horrible selling him I think if he isn't a good representative of his breed. Specially since there aren't very many that I know of.