I have a 30 degree $25 sleeping bag that weighs just over 2 pounds. it is my heaviest bag but thats because it is synthetic.
it dosent meet all your expectations, but is light and CHEAP!!!
not the lightest, but ,lighter than 50oz.
some pics of the $25 bag
not quite as beautiful as a mont bell bag, oh well.
doule sided zipper for foot box ventilation
you cant really see the draft coller and draft tube, but its there
the best way I could think of to show the width of the bag
this bag works great for my dad and my sister. so try it out, if you dont like it, its only $25 and you could cut it up and make a jacket or something.