1 - I fixed a typo.
2 - I fixed the description.
3 - Obtaining runes of levels 3, 4, and 5 is self-explanatory as the "Rune Knowledge" skill increases. There's no point in writing the obvious.
I'm not a fan of detailed texts with formulas in the game itself, so I try to keep the texts as close to the original as possible. That's what the manual is for. Although, for Inga, I took the entire description from the manual.