Well, fortunately, he is 10 weeks old. We had an orphan who's dam died at birth and we had bottle feeds every 2 hours for months! He is now 3 and 16hh (he's a draft cross) and is the biggest brat around! (In a good way!)
Since he is 10 weeks, this is what I would recommend. First off, did the previous owner grain feed him at all? Did he eat beside his mama? If so, you can feed just the pellets, if not, I would recommend soaking the pellets or feeding him a foal feed soaked in the foal replacement formula. Make it very slurpy like you would for an old one. Mostly formula with a little bit of pellets. As he gets older and can "eat, chew" better you can give less and less formula and more pellets/feed. Remember that some foals have to be weaned at around 3 months because mama is being too pulled down. So he should do fine. Be careful giving him the peptobismol. Too much can cause colic. Check with your vet for recommended dosages.