Hi A.,
This sounds like my daughter to the T.. I found that nursing her to sleep actually helped the situation. Yes it may not be ideal, yet your son loves his Mommy and feels comfortable falling asleep while nursing. IN my opinion that is normal. Babies need love all of the time. Being that you don't-co-sleep, your son may need more love from you during the day. Babies love to hear their mom's heart beat and feel the warmth of their bodies.
In addition, as far as the naps, have you tried taking your son on a walk... My daughter falls asleep everyday on our afternoon walk.
As far as being in the high percentiles on the growth chart. My daughter is as well in the high 90's and I do nurse her every 2 hours, even now at the age of 6m. And that is only because we have yet to start her on solid food. - a different issue. So your son is very hungry and will def. need more milk being that he is growing faster than the average infant.
Lastly, a little tip passed down from generations in my family.
Babies under 6m old only cry for 5 reasons.
1. Their hungry
2. They need to be changed
3. They are tired
4. They need love
5. They are ill and need a doctors attention.
If you have this list in your mind and check off each item until you find which need the baby is crying for, then you can attend to it.
If Baby is happy Mommy is happy and v.s....
Best of luck, and remember babies need more love than we could ever imagine.