IIRC Level 7 is just Mastery; aka everything is slightly better/cheaper.
The ? will tell you at any level what hasn't been used yet, sorta. If anything is blacked out and described as an item rather then what it does, there is your first clue that you're not done yet(IIRC anyway; I recall that IC2 Energy Upgrades are "unlocked" when you reach the correct tier and they just tell you about the upgrade and whatnot).
Second, IIRC there is no way of being knowing how "Over" a level up you are, the upgrade tome only tells you how close you are by counting down to 0, and when it reaches 0, if you have used that whole tier, you level up. So if it shows you 2k+ points, that is the running total of EXP in the tome itself, not how far past level 7 you should be by now. If it doesn't say "0 points until next level" or whatever under that, you're not there yet.
Also the Tome will say it's "Mastered" or something once you reach the final tier.