3) The energy content of the hydrogen tank needs to be greater than the energy content of the fuel tank.
And if you were going to add such a huge hydrogen tank to the car, and keep it filled, it would be simpler to use the hydrogen itself as fuel. Many people have indeed proposed hydrogen powered cars. Hydrogen powered cars in turn don't look like they have a very bright future because battery electric vehicles are reaching mass production first, and because batteries are more energetically efficient than storing/transforming energy via hydrogen.
3) The energy content of the hydrogen tank needs to be greater than the energy content of the fuel tank.
And if you were going to add such a huge hydrogen tank to the car, and keep it filled, it would be simpler to use the hydrogen itself as fuel. Many people have indeed proposed hydrogen powered cars. Hydrogen powered cars in turn don't look like they have a very bright future because battery electric vehicles are reaching mass production first, and because batteries are more energetically efficient than storing/transforming energy via hydrogen.