Why is it that figuring out which form to worship God in is becoming such a sticking point? What’s the best way to get around this "searching for the perfect mantra" hangup?
I would suggest that when you sit to meditate that you focus on your heart center. Perhaps your mantra could be "How shall I love thee"? There is a beautiful chant by Swami Kriyananda that asks "How shall I love thee, How shall I seek thee, How shall I serve thee, How shall I worship thee?", and the answer is "With every breath that I breathe".
It doesn’t matter to God in what form we worship, only that we love God with our whole being. Relaxation in meditation would be very helpful. I’m not talking about relaxing the body but relaxation of the mind. One of my favorite quotes for meditaion is this:
The Secret of Meditation
The secret of meditation lies not in affirming states that are foreign to us, but in reclaiming what we are. It is a process of upward relaxation into superconsciousness. The only effort is to resist restlessness and tension.
The more you seek rest as the consequence of doing, rather than in the process of doing, the more restless you will become. Learn to be restful in activity and you will be able to relax better when you sit to meditate.
From “Superconsciousness a Guide to Meditation”
by Swami Kriyananda
God bless you in your efforts!