Should I post-date my patent application?

Post-dating moves your application to a later date. It can buy time, but it never lets you add new matter, and it can cost you priority.

Is it a convention application or a PCT national phase application?

These claim priority from an earlier foreign or international filing, which makes post-dating complicated. Section 9(3) expressly excludes them.

The honest answer usually needs someone to look at your actual disclosure, your timeline and the prior art. That is a conversation, not an article.