Minimal distance between silkscreen text and edge?
It depends on the boardhouse, but likely they can go all the way to the edge since routing (the board cutting kind) is done after silkscreen.

I often have silkscreen marks that go past the edge of the board (in the gerbers at least) and the boardhouses I use have no problem with it.  The silkscreen goes right to the edge.

That said, if you are doing text, be aware of the tolerance to positioning so you don't end up with partial letters cut off.

Here is a recent example:



This is from PCBWay, a very low-cost Chinese boardhouse.  Notice how they stop the silkscreen about 0.1 mm from the edge.  They did that themselves, my gerbers have those lines go outside the board-edge.