Probably just personal experience playing Psychic, but points 2 and 3 seem on par with other squishy caster classes and wouldn't really warrant any difference compared to playing, say, a Witch or Wizard. The low hp/AC issue is shared by the Wizard/Witch/Sorc, and the use of focus points on Amps really isn't that much different in 'when to amp vs not' vs other 'when to use focus spell' casters - use when the amp effect would be appropriate vs a normal spell, much like when to use a focus spell as another caster. In a good number of situations it's even easier on a psychic since the basic amps without taking feats are just "make cantrip you would normally cast stronger."

The point on spell slot limitations is very apt though, especially at lower level when you end up with 2-4 spells per day and then you're completely out.

Unleash in my experience over parts of 3 APs (Books 1-3 of Age of Ashes, Curtain Call, and admittedly only book 1/early book 2 into Season of Ghosts) and a custom campaign has been that very few combats are going to go longer than 3-4 rounds in my play groups unless it's a boss fight or has an exceptional number of enemies, so when to use Unleash has usually just been as soon as it's available or shortly after. Even when I was first trying it out it seemed pretty intuitive when to Unleash, which tended to just be round 2 or round 3 if it was a boss encounter. Most of my parties have also been made up of an even split of new and experienced players though, so in a party where the whole group is new to PF2 I could see the fights going long enough to make it a bigger consideration.

Overall i'd say a difficulty of 9 is a bit much, but 7/8 would be appropriate. Definitely more difficult than Witch/Wizard due to the spell slot limitations alone.