Geoffreyandme~
I wouldn't worry if he's healthy and happy. And as far as his weight, it sounds like he's done great putting on weight! My dd was 7lbs 3 oz when born and only weighed 19 lbs at a year--dr was totally fine with her weight gain because it was fairly consistant on the charts (around 20%) most of that first year, so she was just a skinny kid. ANd honestly, she ate a TON. Then, at 18 months, she stopped being so interested in food (pretty normal thing--toddlers are so inconsistant), but by 2, her weight was actually up to the 50%. So I really think their bodies know what they need and want--as long as they are growing and there aren't other signs of a problem, don't stress. And it sounds like you are doing quite a bit of solids for his age, especially since he's only been on them for 2 months.
As far as cutting down to 3 bottles--I don't think you should worry about that yet either. I bf, but we stayed at 4 feeds a day until she was over a year, then slowly dropped them as we began to wean over the next 2 months. Since they say that until a year, breastmilk, or formula, really is their main source of nutrients, I think the more they get, the better. THis is the time to introduce foods, slowly, but they don't really NEED them yet, so you're doing great.
~Kim