"The problem is that there just is no definitive answer to anything."
This realization can lead to a profound truth; congratulations for seeing this. Most people look for answers "out there" amidst the plethora of religious dogmas and philosophies. Perhaps the answer you seek is elsewhere, as JamesThomas suggests.
"How do I go on with my life without this need to KNOW?"
Another stunning realization! Yes, the "need to KNOW" is the driving force for those who are seeking answers. Understand this: Every "need to know" and the compulsion to fulfill that need is what keeps the answer from being discovered. Sounds paradoxical, doesn't it, yet it's true.
There is something so basic, so simple, so pure, yet so obvious that it gets overlooked by most people, and that is this: What you seek is what you are in REALITY. What you are seeking through religion and philosophies is the basis of your very existence in this very moment. You are peering out of it with every glance you take, and that is consciousness itself. With every sensation, thought, and feeling that registers upon who you take yourself to be, consciousness/You is drinking it all in in silent stillness.
May I be so bold as to suggest to you to discover the nature of consciousness, and in doing so you will not only discover the truth of what you really are, you will discover how life goes on without the need to know. I echo JamesThomas's suggestion of reading The Power of Now, by Eckhart Tolle. He has a way of leading you back to re-discover to the truth of what you really are that is simple yet life-changing.