Some tips from Tohei Sensei in my October 2001 visit to Japan:
Mind and body were originally One.
Do not think that the power you have is only the power you ordinarily use and moan that you have little strength. The power that you ordinarily use is like the small, visible segment of an iceberg.
When we unify our mind and body and become one with the universe, we can use the great power that is naturally ours.
Keeping your eyes open with soft focus initially might help.
Have you tried alternating condensing and expanding? Practice condensing at the one-point until as you say you cannot do it and then start expanding from the one-point until you cannot do it and then start condensing. Just like breathing in and out during Ki breathing you may find one easy than the other. Repeat letting your mind become calmer and more focused. Perhaps over time you will find you can condense a little longer and expand a little longer. Again just like Ki breathing where with practice your breaths grow longer.
To start ki meditation, I like using the hand mind & body unification mudra to focus my mind from my one point while holding my hands up, then drop them to my lap to bring my focus solidly to my one-point and begin condensing and expanding.
With a sleep deficit, or when you have a sleep deficit, my opinion is that Ki breathing practice would be a better to do than Ki meditation. Ki meditation needs IMO a well rested body.
Don't try to over do it. Perhaps, given what you have said, 10 minutes ki meditation followed by 10 minutes ki breathing is quite enough to start with. Try that for a while and put the extra time to good use by doing some slow stretches of where you tend to be the most tight. Over time you may begin to feel quite able to go longer, that is the time to do so. I would be biased toward more ki breathing (15 min ki meditation - 25 min ki breathing), but that's pretty personal.
[See also: Craig's list of resources for Ki breathing and meditation]