It has been a while since I played Anima, but my last character was full of Psychic Powers, so let's try to answer the question as in-depth as possible.
Short answer: yes you can.
You can split your potential into groups of whatever amount you like, subject to a minimum of +10 for any one group; it does not have to be equal parts, so you can go with 30-10-10 and the like.
On the use of psychic powers, this is the paragraph in Spanish (page 194 in Spanish book):
Si un personaje quiere utilizar mas de un poder por asalto, es capaz
de hacerlo dividiendo su potencial psíquico. La division se hace
libremente y cada jugador puede otorgar mas puntos a los poderes que
mas le interese potenciar.
The paragraph in English: (page 192 in English book... ahh I believe (I don't own a copy and I had to ask some friends for this))
Characters wanting to use more than one Power per turn divide their
Psychic Potential [between] the Powers they want to use. They are free to
allocate more points to those Powers they wish to enhance the most.
Bonuses for specific powers (like having +40 on Psychokinetic impact) only apply once, but I believe you can apply them for whichever use you like, although you MUST spend at last 10 of your “base” potential.
There is an advantage that even gives you +10 for each split, although I understand it may have been corrected so it only gives you +10 on each split and each power (so the second time you use Psychokinetic Impact it won't give you any bonus).
You can target whoever you like with the different uses of your power: you are not constrained to use it on the same target. You can, for example, attack two different people with psychokinetic impact and then use the remaining 10 (in the example above) to try and get some kind of shield or whatever you like.
If you attack the same target multiple times it (that is, the target) will be subject to the multiple attack rules and penalised with a -15 on its block/dodge (unless the target doesn't use those rules "normally", like Magic/Psychic/Ki(some) shields or damage resistance creatures) for each attack past the first with some maximum; this is not a Psychic rule, just the basic combat rules. Remember the invisibility penalty if applicable. If you attack two different people, nothing special happens.
Nothing will happen to you (that is, if you reach the minimum required potency in all your powers): you roll for the potency of the power each time, and then you roll to hit each time, as usual; you just happen to have 5 attacks (in your example).
As for where to find more info on this, I can only send you to the Spanish official site, where they have asked this question a few times.
As for when and where exactly Anima Studio has stated things not found in the rulebook, you will have to look for someone that still has the Bards Circle report of the specific encounter with the fans.
I am sorry I cannot help more.