I'm a little late with this, but we're going to need to qualify Practised Manifester further because it is written extremely poorly (seems a cut-and-paste from Practised Spellcaster). So:
A) You don't get more PP from high stats (seems like a no-brainer, but based on the wording, you would, since PP from high stats is manifester level dependent)
B) An Ardent can't pick a higher-level power known using it (the way Ardent is worded, you can take any power known that you can pay for, and with PM, you can pay for higher-level powers)