You are doing the right amount. He is satisfied because he consuming 3-4ozs per feeding and now sleeps 6-7 hours at night. That is great. He will let you know that he needs more by becoming hungry sooner between feedings or when he starts to drink up the 4ozs in the bottle then add an extra ounce (4-5ozs in the bottle per feeding). As he drinks up to 5ozs then add to 6ozs and so on. What is important is that he is growing (weight and height) at a steady rate.
i have two children. i have a two year old and a 10 month old. i belive if you are feeding your child regularly, you are doing fine. if you child is eating 3-4 ounces every 2-3 hours he is getting enough. also one thing to consider is if your child is gain weight. if he is gaining it there should be no worries. if you are still worried about this you should take him to go and see the doctor. my oldest is 30 lbs and my youngest is about 24 lbs. i personally started introducing solid foods (gerber rice cereal) at 3 months. and i was giving him stage 1 baby foods from 3-6 months and stage 2 for 6-9 months and stage 3 from 9-12 months thats what i go by anyway. i hope this helps.