1. depends on the trainer speacialty.  Not all trainer negate drop. I have seen player get worse in skill  when   you train them, if its random which some of it is.  it nothing  than more reverse elastic effect in the higher skill trained but the kicker is  how many skills  should drop at one time 1-2, but some player 3-4 skills. Is that random. I think not.
2,Pr is not garbage you don't understand the Pr system to say it garbage.. You can recover every salary on the game with arena. You  don't think  more money earned in the playoff  or cup is not  worth the Pr salary. that same as saying a better trainer is not worth it( yes the irony).  But in all seriousness.
 Pr Depend on what you trying to do with the team and the appeal your looking for. Once  we come to understand the appeal your looking for to  create , the money will come through that in arena.  if don't create to the appeal you paid for to  maximize the Profit within the PR guy  . It will not work,  the  profit will be minor.
3,    it example not a exact number. 00001% would be the basic. its an example.  Based on principal of 1-6 trainer level easy to understand not to be confused with  the actual table chart. The price between salaries on trainers  is  based on %.    MY point is   You should not buy a higher level if you have not created any revenue to sustain and income long term . My point.
Not that trainer guide is label 00001 and etc. that was  just basic understanding in %  so you see how your spending and saving.. Exp level 6 trainer does more than basic. 0006%   which  is way higher to afford   than basic 00001%. 
4.  Nothing is a mistruth ,have you tried it. I have so how is it not truthful? Am I not doing what  im saying. lol