| Quote #1
I would not, if I could, here or to-day, embody a record of my later years of unspeakable misery, and unpardonable crime. (2)
William says that his deeds are so horrible, he couldn’t express them even if he wanted to. This inability of his writing to accurately reflect reality is another barrier to our understanding what really happened in his past.
| Quote #2
Death approaches; and the shadow which foreruns him has thrown a softening influence over my spirit. (2)
William may be referring to either figurative or literal death.
| Quote #3
Thenceforward my voice was a household law; and at an age when few children have abandoned their leading-strings, I was left to the guidance of my own will, and became, in all but name, the master of my own actions. (3)
The narrator is used to being in control; he controls and creates the world of his narration the same way he dictated his own terms when he was a kid.