Is there anything in the canon that says that force users can only use these named techniques? I'm not very well versed in the details of the Star Wars Universe. Keep that fact in mind when reading the following wall of text.
As I understand it, using the force isn't like a video game or trading cards - there isn't a set of special abilities that are the only ones possible. The named sets are just well understood, documented, and practiced techniques.
Similar to martial arts (and fighting in general): there are well-defined techniques like Karate, Jiu-Jitsu, etc, but you are also free to just go at the other guy and hope for the best. Special techniques are preferred because it gives the fighter better focus, flow, and awareness.
If you're performing some particular Karate block, it will (by definition) prevent you from performing a certain set of attacks - be that through bad positioning, balance, or simply bad flow. That said, there's nothing preventing you from doing something outside those defined moves. You could just go up and kick them in the crotch to disable them - although you might fall over in the process.
My understanding was that the force is similar. The Jedi and Sith have their sets of moves, blocks, and other techniques that promote flow and awareness. However, why couldn't one perform a sort of makeshift combination technique depending on the situation? Why would a Sith have to use "Force Stealth" or "Quey'tek" specifically?
You mention that War and Death already cloud the Jedi's vision - perhaps Jar Jar has found a way to redirect that around himself in such a way that lets him perform other techniques, apart from self-control and trust in the advantages to keeping with a well-defined practice?
IMO, this actually fits best with the theory that Jar Jar isn't really Sith or Jedi, but something in between. He doesn't care too much for the techniques of either party. He sees no problem with makeshift or unconventional techniques - after all, he's powerful enough to use the Force without relying on Jedi or Sith technique. He knows how to keep from "falling over" if he tries to kick them between the legs. This also explains why Jar Jar seems to be the only one to mimic Drunken-Fist style: he's distinct from the Jedi and the Sith in that way.
Even if you don't consider him to be a force user, consider how he fights compared to every other character in the movie. His style (and most of his movement) isn't the practiced choreography that the rest of the characters in the prequels use - he's much more erratic and appears to be improvising (even more so than Anakin on the control ship).