You are asking a lot of questions which are all subjective. They can be honestly answered, why would you NOT want to do those things? The argument can be made, with all sides being equally right, that discovering 1000 mineral deposits deserves a medal for looks, for promotional value, and doesn't deserve a medal since the intrinsic value to the Empire is all the reward needed.
So what do YOU want to do with medals? Use them not at all, CORRECT decision. Use them as acknowledgement of a threshold, action, battle, campaign, theatre, CORRECT decision. Use them as a means to "fast track" promotions, CORRECT decision.
Without knowing how you have the game set-up it is hard to say on the promotion points. Overall each rank has a minimum threshold point, and then the points get reset upon promotion, with the next rank requiring more points to obtain then the one prior to it. If you have political turned on, then that hidden number is taken to account by weighting the promotion points accordingly.