I’m surprised a Japanese history junkie agnostic like yourself hasn’t found liberation in the teachings of Nichiren as practiced by the SGI. Faith is not a choice, it is an inherent power. What matters is whether the object of your faith creates value in your life and thus strengthens your power of faith. Also, I agree with other comments here that you are stuck in dualism — God vs No God. The concept of a non-personified mystic law of the universe offers a middle way.
On Attaining Buddhahood in This Lifetime
If you wish to free yourself from the sufferings of birth and death you have endured since time without beginning and to attain without fail unsurpassed enlightenment in this lifetime, you must perceive the mystic truth that is originally inherent in all living beings. This truth is Myoho-renge-kyo. Chanting Myoho-renge-kyo will, therefore, enable you to grasp the mystic truth innate in all life. — The Writings of Nichiren Daishonin, page 3 (Written to Toki Jonin in 1255)
Also, it seems that you suffer from dualism concerning the concept of faith itself. You seem stuck between Faith vs No Faith. This problem arises when one defines faith as a belief in something that can not be proven. I submit that faith is instead simply a natural power possed by all sentient beings. While many can cross the important threshold of the “accepting responsibility” part of karma, few follow through with the “take action based upon the unlimited potential of the eternal moment” part. This is called being chained by one’s karma, or as some famous Greek once said: being as rational as our emotions allow us to be. If I know what I want and how to get it then I just do what has to be done to get it, simple. Many times, though, we don’t know what to do; or worse yet don’t even know what we want. Other times we know what we should do, but we just can’t seem to do it! Our minds get clouded with delusions; we make excuses instead of taking action. Buddhist practice is about allowing pure wisdom to well up from the depths of our lives in the present moment. ‘Just do it!’ is the call to substitute faith for wisdom when faced with seemingly insurmountable obstacles; and REAL FAITH IS ACTION, not belief. If a faith practice is strong, little belief is required by the practitioner. Healthy belief naturally grows from actual proof. So, yes, just do it! Our lives are a laboratory experiment. If the faith action you employ doesn’t lead to progress try something else. Faith actions must lead to actual proof! If they don’t, then their premise was false; their action weak. The key is to be willing to change your object of faith if you are not obtaining your desired results.