Augment: You can augment this power in one or more of the following ways.
- If you spend 2 additional power points, this power can also affect an animal, fey, magical beast, or monstrous humanoid.
- If you spend 4 additional power points, this power can also affect an aberration, dragon, elemental, or outsider in addition to the creature types mentioned above.
- For every 2 additional power points you spend, this power can affect an additional target. Any additional target cannot be more than 15 feet from another target of the power.
There is no limit on the amount of augmentations that you may select when manifesting a power, subject to the normal limit that you may only spend an amount of pp on a single power equal to your manifester level. These augmentations grant you additional options with the power, and you can select them any number of times - selecting option 1 twice and option 3 once allows you to attempt to control two animals, for example, which the power does not natively allow.
That said, I can't find anywhere in the PF psionics rules where augmenting a power increases it's saving throw DC. This is what I can find on DCs in PF Psionics -
Saving Throw Difficulty Class: A saving throw against your power has a DC 10 + the level of the power + your key ability modifier (Intelligence for a psion, Wisdom for a psychic warrior, or Charisma for a wilder). A power’s level can vary depending on your class. Always use the power level applicable to your class.
The augmentation section doesn't mention anything about extra power points being spent on the power changing the power level, neither does the power level section. A power's level is determined by what level it is listed as, not how many points you spend on it. While some powers do increase the save DC of the spell via augments, Mind Control does not appear to be among them.
This may also help you understand how augmentation works, given your confusion over how many could be selected or how many times -
Many powers can be augmented in more than one way. When the Augment section contains numbered paragraphs, you need to spend power points separately for each of the numbered options. When a paragraph in the Augment section begins with “In addition,” you gain the indicated benefit according to how many power points you have already decided to spend on manifesting the power.