I would stick with the doctor's advice on how much milk he should be having, but as for solids, every baby is different. I would decrease the amount of solids in the morning, and then add a small lunchtime meal, and decrease the amount of solids for dinner. I did this for DD because I wanted to go to three meals and get into that habit, but didn't want her to be too full. And you will end up on a 4 hr + easy schedule. Here's how our day looks to give you an example.
7:30 am wake
8am bottle 5-8oz
9:00 or 9:15 am solids 1 TBS oatmeal, 2 oz veggie
10 am nap
12:00 or 12:30pm bottle5-8 oz
1:30pm or 2pm solids 1.5-2 oz yogurt, 1.5-2 oz fruit
3:00 or so nap
4:30pm bottle 5-8oz
5:30 or a little after solids meat w/2oz veggie, or same as breakfast
7:00 -7:30 pm bottle 7-8oz bottle
8pm bed
I'd love to say she eats this great everyday, but sometimes she seems fuller than others. Usually breakfast gets the most bottle and most solids. If by lunch she doesn't drink a good bottle I will give her a good amount of solids. Dinner, if she didn't have a good bottle will be small, so that she eats a good bedtime bottle. She also has sips of water with her meals.