Firstly, I share your frustration with the way the system refuses the lineups. This is my biggest problem with the game as I seem to be fighting the board on a daily basis.
Regarding your players, the small difference of 2 in their position experience is negligible. This accounts for 2/1000 *0.75 balls on their trainable skills, which amounts to 0.0015 on each skill.
The main reason for the difference in rating between those 2 players is that Eng has an extra 0.6 Tactics.
Personally I would like to try and persuade Vincent to lessen the current restrictions, but I think this has been discussed a lot in the past.