That is not the origin of the term. It comes from a desperate act of defense intending to leave an attacker you can’t beat in open combat with nothing to forage or pillage, forcing them to rely solely on their over growing supply train. Most armies would only ship in supplemental food and supplies while largely living off the land.

IIRC, the biggest uncertainty is about the singularity. I don’t know if it’s still true, but my understanding was that the consensus is that it isn’t really a true point of infinitely dense mass. That is how our current models say it must be, but many assumed our current models are incomplete and that more accurate ones will show that it must have some volume. And given the extreme nature of them, any updates to our models might have some significant repercussions in other aspects of them too.

Time is relarive to your frame of reference. You are always the source of your own frame of reference, so you can never feel the effect of time dilation on yourself. At worst, it would look like the universe outside the horizon started to accelerate to unimaginable speeds. But you would never feel trapped in an unending, at worst that is simply what it would look like to us.

Dietary calcium is great for preventing stones, actually. Calcium is bound to a couple different things that cause stones, but the body actually makes those things specifically to bind with calcium. When it happens where it is supposed to, this is a good thing. If you are low on calcium, these things get flushed, and may get trapped in the kidney. Then any calcium that passes through may bind to it. Having higher calcium intake helps prevent them from building up in the kidneys to begin with. Though extremely high amounts of calcium from vitamin supplements etc can increase the risk of getting stones, but high calcium diet is one of the best defenses against them.

It is actually not an excess of calcium that’s usually the problem, calcium deficiency is actually a greater risk for most. While yes, the most common types are both chemicals that are in part calcium, the body is meant to produce them, just in different parts of the body. Usually, a deficiency in calcium allows those other compounds that should be used up in other places to be flushed through the kidneys, possibly building up. Then incidental calcium that does move through the kidney binds to them there. Higher dietary calcium intake is associated with a sharp decline in stone risk, though extremely high intakes from vitamin supplements etc do increase risk. But in general, it is an excess of the things that bind to calcium that are the things to avoid, apparently almonds are pretty much the worse thing ever, with a fairly distant second being chocolate.