Well, yippie, I have a few things I could say about this : )
First off, this is all IMO's, and there are a bunch of people on these forums who seem to have quite a bit of experience. My experiences may not be yours.
Anyway, back to your topic. First, the "wavy" feeling when Moving of Yin and Yang sounds like somethings I've experienced and there is a topic where people talked to me about it: http://www.learningstrategies.com/forum/ubb/Forum9/HTML/000942.html
The way you describe your experiences with Breathing of the Universe reminds me of something I used to do: earlier in my practice I seemed really concerned with 'holding onto the Energy'. This was a struggling point for me and something I worked through. As I mentioned in the post linked-above (I think I mentioned in that post, oh well), I now think that my struggles with this were the results of removing blockages. Sometimes it seemed like I could feel this mental pressure, and I just knew that I was about to break through a blockage. Sometimes, during these times of pressure, I would feel obsessive or anxious. I knew I was about to break through -- and one of these blockage removals resulted in one of the most 'profound' or intense spiritual experiences I've ever had.
To me, it seems that your capacity to hold more Energy is dependant on the removal of energy blockages. Mentally struggling and straining to hold onto the energy doesn't make too much sense. It's sort of like that phrase in Star Wars 'A New Hope' - Leia was talking to this empire person about the errors of tyrannical ways. Something along the lines of "the tighter your grip, the more star systems will slip through your fingers". It seems that way with Energy and Qi Gong, the tighter your grip the less able you are to have a larger Energy capacity.
Do use the tips in the Qi Gong manual - like the 30 minutes before and after tips.
I highly suggest you continue doing the practices. Do not stop practicing Breathing of the Universe just because your experience is currently something different than what you expected. RELAX relax relax. The fact that there can be good, better and best is very comforting. You can't do the exercises incorrectly, only good, better and best. You may find that when you Let Go, and trust the Universe you will recieve a huge amount of clarity. If you are feeling uncomfortable or mentally disturbed while doing the exercises - DON'T STOP DOING THEM. Keep going, from what I've read, it's during these times that the most progress can be made.
Trust the Universe.
The Love Energy.
Let Go.
Relax.
You may find your experiences changing as you continue.