Does this seem sincere? [I Am Married To A Narcissist]

Really, I'd just need background information about the shit he's said and did. Personally, this doesn't seem substantive because he doesn't directly address the harm he caused to you and he characterizes his bad behavior as "holding grudges," which is basically saying that whatever he did was provoked. If he's deeply mistreated you or if he's truly a narcissist as you say, then this whole post of his is hogwash. I also think it's a case of asking for redemption without making any firm promises and that's a red flag in my eyes.