A) It's a balancing act between youth academy and form training. Remember to buy some decent players you aren't going to keep but will manage to sell for more than the 30000econ it costs to bring them into your club. Even a little boost is welcome.
B) If the midfielders and strikers went up last season, they may struggle to go up again after a great previous season. Usually you should be able to get them to 10 though!
C) The all-rounder one is a bit useless really, they play better than anyone else if out of position but still only about 75% of their skill I think? There's a site I found rating the usefulness of abilities (maybe it was on the xpert eleven site). I'll see if I can track it down.
A bit old, but: @dan\-likes\-trees you might want to have a brief look as well.