“Personally I accept rebirth as a plausible possibility but on the other hand, it should be possible to evolve within Buddha Dhamma without having an unwavering faith in rebirth.”
If there is no rebirth and law of kamma, then there won’t be any new causes and conditions to shape this world of 31 realms. Sansara will never end. And because sansara is never ending, there will always be causes and conditions to shape the world and sustain sansara itself. We ought to have unwavering faith in rebirth.