You've already heard...you can't compare across all those different scales.
Like one of the PP suggested, have your LC weigh him before and after nursing so you have an idea of how much he's getting. For me this was especially important once I transitioned from bottle to breast. When I was bottle feeding the pumped milk I knew exactly how much she was taking in. When I moved to breast I was blind to this and of course nervous. But I had the LC weigh her pre and post nursing and I realized the little one was taking in a very good amount!!
After that I pretty much just let nature run its course and she's been gaining weight perfectly. But it was really reassuring to have that pre / post weights done by the LC and whenever I went to the new mom support group I'd have her weigh her just so I could be sure.
As for the sleeping...it's normal for them to sleep tons. DD slept from the time she finished burping to the next feeding. Unfortunately, the next feeding was occuring 2 - 3 hours later
'round the clock. She also had her daily evening crying spells but that subsided about a month ago (thankfully!!) It was heading into her 3 month check-up that she started having shorter stretches of daytime sleep and longer periods of being awake and social.
Hang in there!! I'm sure little Aaron is thriving just fine!