regarding the level max, you could do a level 40+ (or 60+ if the last level ends up being level 60 for example).

It would mean that once you reach the max level, the exp bar doesn't fill up, and instead you get a new "level cap" which is much higher than the exp needed to get from level 39 to 40 (like 5 to 10 times higher maybe, or more if you want).

once you reach it you get to level 40+ and nothing changes except your energy bar is refilled, and you get another "level cap" which require the same amount of experience to fill up, ad infinitum. This way players who are at max level whould not feel like any reward of exp in the scenario is wasted (perhaps it could also refill the fight bar).

It's a system that was used in the game "marvel, avengers alliance". I guess you can look it up if you are interested.