miracle, this is how it works... (at least from my past experience and recent ticket purchase.............)

since you have already figured out the checked luggage, all i have to say is to other ppl, please stop giving ideas and suggestions if you have no clue about it...or at least make sure you were talking about long time past scenerios. Otherwise simply give links and details from original websites. remember little knowledge is dangerrous. No hard feelings, just a suggestions..

Miracle, regarding hand carry, on most airlines connecting through Asia, and middle east will allow one hand carry (within the size specidifed) and one small laptop or personal item.
Since you are flying from USA, I have hardly seen them check the weight of ur hand carry. The rules apply for USA airlines and they will allow u to carry 40 lbs. But believe me, they will check the size (dimensions) of ur carry on if they see that it is little bigger. AT airport, they have that carry on check thing (i dont know what is the name) where they will ask you to put ur bag inside and see the height and nake sure it fits. You can help to squeeze it.
when u about to borad in Baharien to Nepal, they might asked to weigh, but then its irrelevant. Tell them this was ur weight from original destination and you have not bought anything. Frankfurt is not a problem.
In worst case, I took a couple of things out carries in a seperate baf until i reached plane and again put back in hand carry. So couple of unused platic bags is helpful to carry. Just in case.
When flying back from Nepal, they will not allow to carry anything more than 10-15 lbs which is like 5-7 kg, which in my case was almost the weight og the hand carry. Tara from Nepal you can make small couple of plastic Pokas if hand carry is heavy and make sure u put that back in hand carry only when u at the inside of plane.

hope this helps