Buddhism: Morality & Biology

I have relapsed out of Buddhism two times in my past. Currently, I am between reconciling and rejecting it yet again. I decided to make this post to ask questions that I feel will help me either reconcile or reject Buddhism. I have categorized my questions into two areas: morality and biology. Before I write my questions below, please note the following information: I was/have been part of the Theravada Mahasi Sayadaw tradition under Yuttadhammo Bhikkhu's teachings and have studied both Buddhism and science in the past as a vigorously dedicated layman in both fields. Section 1: Morality 1. How is it possible that those who achieve Nibbana are morally infallible? 2. How is it that certain mind-states are objectively unskillful (evil) or skillful (good); wouldn't that be subjective to say? Section 2: Biology 1. How can there have been past Buddhas if civilization/*Homo sapiens* evolved recently (archeologically speaking)? 2. How do the planes of existence and rebirth make sense amid the heavily (as far as I understand) supported theory of evolution? Thank you for your time and may you be well.