Q: Should it not be reduced to a single point analysing the unanalysable, elementary and vaguely perceived and elusive ‘I’?
Yes. It is really like gazing into vacancy or a dazzling crystal or light.
Q: Can the mind be fixed to that point? How?
If the mind is distracted, ask the question promptly, “To whom do these distracting thoughts arise?” That takes you back to the ‘I’ point promptly.