You seem to confuse the damage output with the damage dealt here. I will use my own stats on zed as an example here since i know those stats by heart.
So, i get 418 bonus AD on zed and my Q has 100% bonus AD and 235 bas damage. So, with that in mind my Q will do 235+418=653 points of damage. I will keep the calculations simple here because i am too lazy to use a calculator and i might forget something and so i will not take into account any form of bonuses from masteries or whatever other buffs. So, that 653 value is the raw damage output of one single Q. Now, if they have lets'say 100 armor and you have no armor pen, their damage reduction is 50%. So, your Q will Deal 326 damage instead of the raw value of 653.
So, your damage output is the raw value of 653 but the damage dealt in this instance is 326
So, in the example of the lifesteal, no matter your damage output, no damage will be dealt to kayle because, as you correctly stated, she is immune to any form of damage and therefore she will take no damage. So, in that moment, you will the damage dealt will be 0 while your damage output might be whatever it could be depending on your build.
Now, i assumed you are american because you play on NA and unless you like lagging, which i really doubt, you wouldn't be anywhere else other than the U.S or Canada.
About perfect scores, i got perfect score in english in all written tasks but fucked up big time in the Essay and in speaking, i got really really nervous, pardon me, i was 14 :P
If you've seen any other of my posts, you would know by now, my essay skills are worse than the worst... I barely passed the essey exam... ye, i feel bad about it but don't care to change it either, it's not my native language anyway, i only use it to post on the boards and when i watch movies and in game to chat...
And no, i don't expect you to measure distance in miles and call rugby football.... btw... how do they even think this thing is football? Do they even kick that thing that it also isn't a ball? So, if not from the US or Canada then... where? you said NA is the closest to you so..