The below paragraph is from a book, Man's Search For Meaning.

To get the exact meaning of the last sentence, I looked into Webster's Leaner's Dictionary. And of the six meanings, I think it's #2 meaning that fits into the original sentence. Am I right?

Yes, he was beginning to understand. A grin spread slowly over his face, first piteous, then more amused, mocking, insulting, until he bellowed one word at me in answer to my question, a word that was ever present in the vocabulary of the camp inmates: "Shit!" At that moment I saw the plain truth and did what marked the culminating point of the first phase of my psychological reaction: I struck out my whole former life.

▸strike out [phrasal verb]

1 baseball a strike (someone) out or strike out (someone) of a pitcher : to cause (a batter) to be out by pitching three strikes

▪ The pitcher struck him out with a curve.

▪ The pitcher struck out the first two batters.

b of a batter : to make an out by getting three strikes

▪ The first two batters struck out.

2 strike (something) out or strike out (something) : to remove (something) from a document : delete

▪ The editor struck out the last paragraph.

3 US, informal : to be unsuccessful : fail

▪ “Did you get her phone number?” “No, I struck out.”

4 : to begin a course of action

▪ She struck out on her own after graduation.

5 : to try to hit someone or something suddenly

▪ He struck out wildly with his arms.

— often + at

▪ He struck out wildly at the police officers.

6 : to make a sudden and angry attack against someone

— often + at

▪ Both candidates struck out at their critics.
Stenka25of the six meanings, I think it's #2 meaning that fits into the original sentence. Am I right?
I would say that you're right. Yes. erase, delete.

Students: Are you brave enough to let our tutors analyse your pronunciation?
Thanks as ever, CJ.
I'd say #3.

#2 would mean he removed or deleted his whole life.

In baseball, when you "strike out", you have failed to accomplish your goal (of hitting the ball and getting on a base.)

He refers to seeing the plain truth now, indicating he was doing the wrong thing/failing previously.