I doubt HEAT would create that large of an explosion. The power in those is not the amount of explosives, but that they use a shaped charge. It seems they used normal HE is this clip, but the explosion has too much fire to just be HE.
Its calculated after income, so you will only receive the bare minimum needed for basic living. However if you want to live in a small apartment with no actual disposable income there is nothing stopping you. Thats actually how some students get by.
There are many social programs, but the biggest one is "Expense assistance", where the state will make sure you have minimum amount of money required for living after income. In practice it's around 600-1000€,just enough for the cheapest rent and cheap food. However that's all you need to get back on your feet.