As a matter of fact, hydrogen has rather low energy content, if molls are concerned. The only advantage of hydrogen is that it is light.
Well, known fact, the hydrogen is the lightest element in universe.
What does it means in practice that one needs extreme pressures to store hydrogen.
The same energy contained in e.g. propane need about 4x pressure in hydrogen.
Yes something like that. Let's see 140 to 200 psi for liquid propane depending on temperature vs 5000 to 10,000 psi for gaseous hydrogen. I think that is a little more than 4x the pressure. Or if you want to get propane like range you need to cool it to -430 F and then have constant flammable off gassing... and once it heats up it is all gone whether you put any mile on your vehicle or not.