re: Players missing treasure
There's nothing wrong if the players actually miss some treasure (a.k.a the level +x magic items).
The DMG states that as long as the players are at the +2/-2 range of expected value, you won't see much difference in actual battles. Basically, if the "expected" value is that a PC hits on a 11, the weaker guy hitting on a 13 and the stronger character hitting on a 9 isnt going to "break" the system.
The PCs only NEED 3 slots filled out and with 5 PCs, this comes to 15 slots.
The treasure reward system insures that for evey level, the party gains the equivalent of 2xmagic items of their level in monetary reward.
Across 5 levels, this means that 10 of the 15 slots can be filled by the players themselves. The 5 slots not filled would still only be under by +1 which the DMG itself statees won't make a difference that much.
Thus, you don't actually have to give out the entire 10 parcels for every level.