Yes (and yes)
I understand that "total" does mean "maximum". I cannot think of any other reason to say
The duplicate has half the total Power Points of the caster,
The duplicate has half the Power Points of the caster,
On top of that, assuming that "total" means "current" would mean that the power produces a different effect depending on when it is used, which is something that does not happen with any other power (in particular, with the other versions of Summon Ally, like summoning ogres or sentinels).
UPDATE: Clint confirms in the official forums that the Mirror Self has half the maximum power points of the original caster, rounded down.
[the Mirror Self of a legendary caster] would have 17 Power Points, half
the caster's total of 35 PPs (not his current level).
And yep, rounded down.