The factotum uses normal metamagic feats, as explicitly stated at the end of the arcane dilletante ability description.
"If you wish to enhance a spell with a metamagic feat, you must apply the feat when you prepare the spell. In addition, you must be capable of using a spell of the modified spell's level."
Ignoring the sloppiness on spell level vs spell slot, this is pretty clear that you use Maximize Spell and it increases the spell level normally.
As to whether Maximize SLA works... ummm... does Ability Focus: Arcane Dilletante work? There was just a whole thread about similar issues, and the result was unclear (to me, anyway). For balance reasons, I'd say no, Maximize SLA doesn't work, but that's ruling on function, not form.
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gnfnrf