I know that the amount of training points from training goes down with player development.
My player with rating 160 and training speed 195 get 14 training points per day
My player with 180 and training speed 196 got 12-13 points...
But last week I bought premium player from auction with 225 rating and he also get 12-13 training points per day...
So is there any limit of "lowering" training points after some star rating? May be after 200?

Nice job testing. I can say I don't know for sure but it would make sense. The reason that training is slowed is due to the improved training grounds you should have. However, since we haven't had any chance to upgrade training grounds it would make sense to not continue to make training more difficult.