OK, after some more time spend researching, i think i might be able to answer some of mine questions. If is anyone interested...
- i havent found any zero pose, but i created my own using some kind of calibration. I saved rotation matrices for my chosen zero pose (let's call these Mz), made these matrices trandposed (MzT) and I multiplied all the next matrices kinect gave me (let's call these Mr). It means I calculated matrices for further use this way: M = MzT x Mr.
- I used the conversion from link in 3. question for Rxyz order and all worked well, it means the rotation matrices given by kinect probably have the order given in the question. This should be answer to the third question as well.