Wow your mediums are a lot larger than the ones I get. Mine seem to average around 140-170g. Your larges are a little bigger too. Mine average about 180-220. Now that's for the place close to me. I reptile shop where they have all the quails, rabbits, gpigs and chicks seems to run about the same as yours. No idea on the smalls as I have never weighed those.
I honestly think your snake is going to smaller than 8-9' with that feeding schedule. I'd guess he tops out at 7' but who knows really as half seems to be food intake and the other half seems to be how the genetics play out.
Problem I see with ours is they aren't full SD. So I personally think it is hard to really put a number on their size. I mean Gene is a perfect example. He's 25% SD, 25% dwarf and 50% mainland and he is like 5'. But anyways, it will be interesting to see how all guys' and gals turn out in 2 years.
You could do quails now. I was feeding Caesar like 3 week old quails I think when he was on small rats. They are about the same size as baby chicks. Last time I looked at the shop, the 7 week old quails were about the size of a large rat but I doubt meatwise, just purely on the thickness of them when I was feeling them up. I'll have to pay more attention to the age when I get there. I usually just look at the bags and say "Yeah, that one there" lol.
The rabbits and gpigs, the smallest ones I saw were way to big for Caesar. I mean he probably could have downed it and I was told by a lot of retic guys on Retic Nation FB that a 5' SD can easily eat 2 large rats or a baby rabbit or gpig but I didn't want to chance it.
Oh and stay away from the Retic Nation FB page. I got scolded for feeding Caesar medium rats when he was 5'. Everyone pretty much said I was underfeeding and starving my retic which was why he was pushing and scraped his chin up. Or he was looking for a girlfriend but since he is only 9 months old, they said I was starving him. With feeding yours smalls, I'm sure they would rip you apart on that.