Regarding your questions about various names of God, we have nothing to do with Jehova, Allah, Jesus, etc. If somebody else wants to chant in this way it is all right, but nobody is chanting Jesus etc. If they like, let them do that but as far as we are concerned, we should be satisfied with the Hare Krishna Mantra and nothing more. We have registered our association particularly under the name of Krishna. God has millions of names undoubtedly, but we are especially concerned with the name of Krishna because we are in the disciplic succession of Lord Caitanya Mahaprabhu Who chanted this Holy Name, Krishna. Everyone should be particular to his particular disciplic succession or sampradaya's regulative principles. This is required, as much as there are many different political parties, although every one is meant to serve the country.
So far as you not completing your chanting, I think this should not be a regular practice. If by chance you miss to finish in one day, that is a different thing. But as far as possible we must try to complete the prescribed number of beads. You should try to chant at least 2 or 3 hours every day. We have got 24 hours at our disposal, so for chanting we can find 2 or 3 hours without any difficulty. Simply we have to adjust things in the right way.
Regarding utilizing intelligence in devotional service, intelligence should be confirmed by the Spiritual Master. Therefore we accept the Spiritual Master for guidance. You should not depend on your own intelligence. Just like a child requires a parent to tell him the correct thing to do, similarly, a strict disciple should always use his intelligence in conformity with the instructions of the Spiritual Master.