Btw, I recently found a bug in the time played in each team values in etpub (mapAxisTime / mapAlliesTime). It is not computed when players are in limbo, so the more a player spend in limbo, the less accurate these values are. Consequently, the PRW can't be accurate either. Chances are that this bug is still present in latest silent.
Yes, ETPub's KR takes skill of killed player into account. Making "easy kills" on noobs won't improve your KR much, but killing a much better player than you will improve your KR much more.
KR is independent of PRW, and doesn't really make sense in a multiplayer game since it takes into account only the attacker and the victim, much like an independent 1vs1 game. But PRW is quite interesting imho. PRW also (optionally) takes the difficulty of the map into account.
If you're interested in knowing more, look for J.Menke's documentation: "A Bradley-Terry Artificial Neural Network Model for Individual Ratings in Group Competitions", and "Hierarchical Models for Estimating Individual Ratings from Group Competitions" (the later being an updated version). Strong background in mathematics/statistics recommended.