Interesting project. Your choice of bombs is pretty much correct. A 100 pound bomb is about 60% the size of a 500 pound bomb (1/(cube root of 5). By using 1/144 bombs you have selected bombs that are 50% the size of a 1/72 500 pound bomb. So, pretty good choice...theoretically a tiny bit small but I suspect they are molded a bit too big anyway, which is normal in 1/144 ordnance.