I'm sorry I haven't responded for a little while - I've just been extremely busy with this new foal as you can imagine, LOL! I wanted to provide everyone with an update on how he is doing. I had my veterinarian come out the other day, and we came up with a wonderful "nutrition plan" for this guy. First off - he no longer has diarrhea which is wonderful, thanks in part of the Probios and Maalox. My vet told me not to use Pepto Bismol because it includes aspirin which can exacerbate ulcers - but Maalox does not have aspirin. He's eating like a hog - another wonderful sign.
My vet said that it's okay to begin the weaning process at his age (In HIS specific case) if he's already eating a fair amount of grain, which he is. So we put him on Senior Feed (vet said it's more nutritionally complete than most mare/foal creep feeds). He is also on Grow Colt nutritional supplement and he gets a small handful of Calf Manna. My vet said she's not too much of a fan of Calf Manna, but I could throw some in if I wanted to. He is being fed 5 times per day this week, and he'll be fed 4 times a day two weeks from now.
I asked her about vaccinations, but she said He's too small for vaccines quite yet - and the only thing she would feel comfortable giving him is a tetanus shot.
But he's doing wonderful, and getting into everything imaginable! I am grooming him every day (Picking feet, brushing, fly spray) and it's my hope that he'll turn into a very, very well-mannered and easy to handle boy once he's larger. I'm having to watch him constantly, constantly, constantly... I basically have a new toddler that depends on me 100% to keep him safe, LOL!
Thank you all for your outstanding suggestions. I just wanted to give you an update :)