Suggestion: Unless you intend for each chapter to be a time skip, spend out experience over the game, slowly, a point at a time.
HERO makes for really good slow power development. . .take a power at it's minimum, say 1d6, slap disads on it like a high activation roll to push it down to a cost of 1, so you develop a really unreliable new power, which you later put point after point into until it's a decent, reliable power. . .
Or
Develop a power you already have, but do it 1 point at a time, so it only gets a little better each time.
Or
For powers with point increments of 2+, you train at it, and only get the improvement when you get the 2, 3, 5 or whatever amount of EXP you need to go up one step with it.
It lets characters develop in a more organic manner, where "Spend 10 EXP" ends up with a more leveling feel of jumping up to a new plateau.