This is true, but depending on how you use the hydrogen, you can fly much higher than you would with kerosene. Hydrogen burning jets would fly at around 70-80k

This is true, but depending on how you use the hydrogen, you can fly much higher than you would with kerosene. Hydrogen burning jets would fly at around 70-80k feet, not the usual 35k that we're used to. Not to mention, the weight savings mean you cut down on the amount of fuel you need to carry, so the 'blimp' effect is overstated. One third the energy in LH2 gets you around half the distance as an equivalent volume of kerosene, because the volume of hydrogen only weighs one tenth the mass of the kerosene. So getting the same range means you need more volume, but you need less total energy to get you to the same destination because you're lofting less mass.