I must inform you that you're mostly spreading ignorance or obsolete information with claims like those. Most of the claims you're making are either wrong or many years out of date.
> There is zero elemental hydrogen on Earth.
Not actually true. As I understand it, reserves of natural hydrogen do exist underground, similar to how helium is sometimes trapped underground in certain formations. These could potentially be huge source of hydrogen, although right now it's just speculation.
> Yes, you can produce it from electrolysis, but not only the hydrogen produced this way will never "break even" it's actually much worse than "even" since you then need to spend a whole load of energy to compress it and bottle it.
Since we live in a world of zero priced, and sometimes negatively priced renewable electricity, this is a non-issue. In fact, it's irrelevant. The biggest motivation for green hydrogen right now is the fact that we have far more green energy that we can use for large stretches of time on the grid. We're currently "curtailing" that electricity, which is a fancy word meaning that we're throwing it away. Turning what is in effect a waste product into a valuable new fuel is a big gain.
> Why not...just put the electricity into the existing grid and charge automotive batteries directly? After all, fuel cell cars are electric cars, direct combustion of hydrogen was experimental and extremely inefficient.
Largely because we can't match production with demand. As I mentioned above, we have huge surpluses during parts of the day, but also we have huge shortages at other times. Using hydrogen as a load balancer is an excellent idea right now. We can do this to a certain extent using batteries or pumped water, but we quickly run into the limits of these technologies. Hydrogen can be stored in far larger quantities than any battery in the form of underground salt caverns.
> That brings me to my next point - hydrogen has the smallest molecule of all, which means that it evaporates naturally through any container you put it in. 70kg lead bottle only holds 1L of hydrogen, and it naturally loses all of it in 2-3 weeks. So no underground carparks, garages etc because of the explosion risks.
Carbon fiber tanks have long since solved this problem. We know this since you can buy FCEVs right now, and they are perfectly fine vehicle with none of the above issues. Indeed, I've seen quite a few hydrogen skeptics review these cars, and while they maintain their skepticism of the idea of hydrogen, they seem to be at a loss at describing any kind of real shortcoming in the technology itself.
> But finally - there is no infrastructure for hydrogen. It's like trying to build a network of petrol stations....from scratch.
This is changing. There are now hundreds of hydrogen refuel stations around the world, and many more being built. This is particularly true in Asia, where governments in that region have sponsored huge hydrogen infrastructure buildouts.
> And batteries are definitely good enough to power larger trucks, it's just the cost that's prohibitive(enough cells for a large semi would cost many times more than the truck itself).
There many problems with battery powered semi-trucks. Cost is one of them, and weight is another big one. Furthermore, recharging them in a few minutes is a huge selling point, and batteries cannot deliver on that need. FCEVs are a much better answer for long-haul trucking than BEVs.