Regarding the math of the spell points, defacto, there is no "gap" between slot 2 and slot 3. There are some very powerful level 2 spells and some very subpar slot 3 spells. Thus there is a seemless continuum from 1 to 5.
Recalculate the spell points available according to the following values
Slot 1: 2 points
Slot 2: 3 points
Slot 3: 4 points
Slot 4: 5 points
Slot 5: 6 points
The higher slots are treated separately.
I actually only use points for slots 1 to 5. For slots 6 to 9, the game system treats them separately, and I just use the regular per-day slots for them. This also avoids spamming the spells of slots 6 to 9.
A character can spend 1 point to cast an unknown/unprepared cantrip.