It's a cornish x. "Cornish" game hens you buy are exactly what you are holding there, except they butcher those at 4 weeks old instead of 8 weeks old. Yours is in the 8 week old range.
These birds are raised in warehouses and it can't stand well because of it's fast growth and weight for it's age. I free range mine, and if I did not force them to stand to eat while they are growing, they would rather sit all day long... if the tendons in it's legs are not broken yet, there is chance that he may get up to stand more often. I find raising a few layers with cornish x's keep the cornish on their feet a bit more, and keep the layers calmer... however, this is done on the short term before the broilers get butchered at 8 weeks or so.
I'm not sure what percent protein duck feed has in it, but I would try to get chicken feed if you want to keep it as it's protein should be in the 16-20 range.