There's a few things that jump out at me as possible sticking points. The first thing I noticed is that you seem to be attempting things that have a strong physical analog. "I decided to open my eyes" and "I tried to sit up." When you tried to open your eyes you saw the ceiling. When you tried to sit up you couldn't because you were in sleep paralysis mode. I think when you are trying these things it is your body that is still responding to the mental effort. For instance, when you wanted to see, instead of trying to open your eyes you could simply express the desire to "see". Out of body, you have no eyelids to open and no eyes even! You are only receiving data that is analogous to seeing. You don't have to "open your eyes."
I have been there. Years ago, after reading Journeys Out of the Body and trying so hard to duplicate Monroe's experience, I would occasionally wake up experiencing the vibrations and immediately try with all my might to move my nonphysical arms. This would only break the state and I would feel the tension in my arms from trying to move them.
The other thing that sabotaged my efforts was the tremendous excitement that occurred when I felt the vibrations because I was thinking "All right! Here's my opportunity! Must get out right now!" I would suddenly feel my heart beating hard and a feeling of anxiety which would break the state and simply wake me all the way up. The thing that finally allowed me to succeed was, as Jeff suggested, staying calm and relaxing even further, especially my mind. I just enjoyed the experience and let things happen. And things did happen. I have expereinced an out of body state, lucid dream like states, communication with entities, all from simply relaxing and letting things happen. Later, I started expressing a desire (an intent) for whatever experience I wanted without trying too hard to do anything. This is sometimes successful. My attempts are still hit and miss though. Sometimes I have amazing results and sometimes I reach sleep paralysis, feel the vibrations, and nothing else. This is still satisfying in it's own way though so I don't complain.
Tom has cautioned several times about the hazards of expectations and trying to duplicate someone else's experiences. Yours may be similar or totally different. Have no expectations. Experiment and find what works. Something Tom suggested that I have tried, and it seemed to work, was when you find yourself in that state, simply have an intent to have whatever experience that would be most beneficial to your growth and learning. Tom says the system will help you if it is beneficial for your growth to have the experience. Another thing he said that was tremendously helpful to me was that whenever you reach the state in meditation where you are no longer aware of your body, you are out of body! It's all about where the focus of your consciousness is. Tom's words finally freed me from the expectation of having an experience a la Bob Monroe which amazingly allowed me to do just that and much more. Keep at it. You are much further along than you think.
Here's a link where I recount some of my experiences, including my initial OOBE. You may find it interesting reading at least. viewtopic.php?f=13&t=3754