Jan Jordan Voll, your player looks more a DMC than a DC, and hence the heading special ability might be less useful. But, with this game, you can't be sure. He can still perform better at the DC position.
I have never trained a player for a special ability so far; I never had green pack offers from the browser version. But, in the past, I have bought a lot of players with special abilities. Some did seem to provide a 'bonus' and some did not. I have a DR/DC currently training for DL though using the skill points obtained from normal training and matches played.
How come you spent only 50 green packs? What level are the training drills that you used?