The Buddhist philosophy is already meditated in several of the Veda, Vedantas and other Dharmic scritpures which predates the Buddha. Buddha said nothing new or innovative it was always there the only problem was only scholars had access to those knowledge. It will be absurd to define Sanatan Dharma. If somebody can do it more power to you. Sanatan Dharma is about inclusiveness not about absoluteness. I don't consider Buddha Avatar(god) or anything. The whole concept of Avatar should not be taken literally. BTW you should not run away from your responsibility for the sake of finding truth.