Pictures are good idea. Take some pictures of you old Jamis and new B USA.. side views would be great to compare them.. someone with photoshop experience might even be able to overlap the two and really let you see the difference in fit between the two bikes.

About the bottom bracket and seat position, the seatpost setback may have something to do with the difference between the two bikes.. other than the seat tube angle differences. Personally, I like to have the seat way back from the b/b.. allow better pushing bike forward with legs.

By your need for smaller handlebar, do you mean narrower handlebar or shorter reach handlebar?

Your bad habit of resting in the drop using the aerobar really comfuses me. there is no drop in aerobars in general, the drops on the road bike handlebars are at the end of the bars, far point from stem, even lower postion than the brake hoods.. maybe you've got your terminology confused?