The good thing is that you are getting better and better with flash. The bad thing is that if you're like me, you'll want to try even more. And before you know it, you have 10 different flash units in you paws
As you found out, the PT-1D and PT-2D have some interface with the current batch of Pentax DSLRs (as do the Pentax flashes AF200T, AF280T, and AF400T). For sure they can tell the camera body that the flash is ready and in some modes set the camera's shutter speed. They may even set appropriate aperture in some cases.
About the LCD's blinking - I don't have the K-x, but my guess is that the K-x's LCD will blink if the exposure setting in M mode is not "correct" (this has nothing to do with the flash). With Pentax-dedicated module, when the flash is not ready, the set exposure will result in under-exposure. So the LCD blinks. When the flash is ready, the camera knows that there is a flash attached, so it stops the blinking.
With Ricoh-dedicated module, there is no communication between the flash and the camera, so the camera doesn't know the flash is there, ready or not, and thus the LCD is always blinking.
About flash diffusers, you can make them
real cheap. Don't buy any expensive (read: more than $5) diffuser until trying out your DIY versions. Read:
This thread.
This thread (my post is on page 2).