Healthy turkey weight?

I recently 'rescued' a turkey. I say rescued, cause in my eyes that's what I did. He was advertised as a 5 month old royal palm SQ tom.
Some BYC'ers informed me that he's acctually a 2 month old sweetgrass jake. I knew he wasn't RP the second I saw him, but wasn't sure what he was other than mudy, scrawny, and not well taken care of. He was living in inches of his own poo, crammed in a dog lot with a bunch of bronze turkeys a lot older than him. In a dog lot two small for even just two turkeys. The only thing in there for them to eat was a bowl of what looked like saw dust. They said it was oatmeal. I've seen oatmeal, and I'm pretty sure it wasn't that. And he won't touch oatmeal, so if it was he wasn't eating. There was no water bowl in the pen, I guess they were drinking mud.
Anyway, a month has past. Most of the caked mud has fallen out of his feathers, and he's put on a lot of weight. He's eating high-protein game bird starter with a bit of laying mash mixed in. He's looking much better, and has put on a lot of weight. When I got him, I could feel every bone in his body. He quickly became super friendly, and absolutely loves people. But, it's taking him awhile to physically recover from his chickhood. He was the littlest guy in the pen, and even if he would eat what they had in there, a big bronze tom seemed to be guarding it viciously.
I wish I coulda gotten all the turkeys they had, but only had room for one. Right now, he's living in a 5X10 pen, and gets to come out while I'm out there...it's pretty much just his bed room. He's now three months old, and I weighed him today. He weighed in at 12.5 pounds. Is this a healthy weight? He still looks really skinny, but as a jake I know he shouldn't have his big round tom shape yet anyway.
He strutted and gobbled the first witnessed time today, so I think he's feeling better :-D
Sorry for the long question! Just wanna know what he should be weighing at this point. Being heritage, I don't think he should be supper heavy...but I still think he's not quite where he should be yet. I will take any suggestions I can get on anything. Feed, housing, anything. His name is Griffin, and he's my baby I'm trying to learn all I can to make him as comfortable, happy, and healthy as possible :-D

I haven't actually weighed mine, but it takes a long time for heritage turkey breeds to grow, it can take up to two years for them to reach full size, they will never feel fat as they are not broad breasted. Mine are about 4 months and they are finally looking to be getting somewhere on their growth, they are visually about half the size of my adults, I wouldn't be trying too hard to feed him as you want a slower more uniform growth.

Mine are now eating an all flock ration with some corn and sunflower seed scratch as well as free ranging, the little toms are trying to display when the adults aren't looking, and the females were also displaying and working out the pecking order.