First of all, you look great.
BMI is a terrible judge of fitness for guys your size and fitness level. It just doesn't take into account that most of your weight is muscle. It's too generic a system. It puts me on the upper end of healthy just shy of overweight and I carry about 9 percent body fat. So, my first recommendation to you would be to totally ignore BMI.
Just by looking at your pictures, I'd guess you're in the7-9 percent range of body fat though you might carry a higher number because of subcutaneous fat that you can't really see. Again, you look great - very healthy and athletic.
But I know what you mean about wanting to be more cut. I feel that way too. I think a lot of it is genetic at the point you're at but it could be diet. You say you're eating paleo. Do you cheat at all? Alcohol? Dairy?
The other thing that's helped me get just a bit more lean when I'm already low is fish oil. I take 3 tspns of Stronger, Faster, Healthier a day or 6 tspns of Carlson's. The SFH tastes way better and is more concentrated from higher quality sources.
Keep up the good work.