you can get runes from blue armor drops from charr, and then you can charr salvage kit to get the runes, and put em on armor

Awesome question. I actually (sort of) answer that one in my write up. But I won't make you wait. The answer is as soon as you can. GMike said he was able to kill charr with a lvl 3 mes so I would think it would be an option for a lvl 7 Ranger. I'm at 9 myself but I haven't tried the charr yet.

Suppose I have all the charrs piled up, what lvl should they be when I start killing? My level, a level above me or lvl20 or..?

Also, how much time does it take (I know you can't tell an exact time because it depends on your lvl and the amount of charrs you have) to death level them to the appropriate level?

The time it take is dependent on how many charr you pulled. The more groups you pull that faster you die, the faster they get EXP. But they will not all level at once. at about level 12, one charr group will start to level ahead of the others and the others will not level until that group is killed. I did my death leveling when i was in High School so i would set a DL before bed and in 6 or 7 hours when i was awake i would kill it. I only ever did 1 group of four and i would search for the perfect hunter hunter ashen ashen group as they kill the fastest. You should always kill the group one level above your own, as you will get 1% per charr. Waiting to get them to 20 is a waste because the time it takes you could be leveling another group to one level about your own. hope this helps. If you have any other question just ask!