fix non-significant errors in a manuscript that is not accepted and currently under review after 1st round of revision?
I work in biomedical field so am not sure how vindictive psychology specialists are. The few I worked with are pretty nice, but n=3.

My opinion is definitely option 3. It's not just the p-value that matters, but also i) the statistics itself (e.g. the regression coefficient) could be different and ii) replicability could be threatened as well. If someone would like to follow your work they may be perplexed by your errors.

As for leaving a bad impression. I'd rather get rejected because I was being diligent than getting an acceptance with a flaw that I once convinced myself was trivial, but occasionally came up in the back of my mind. Just bad flavor.

I'd say no need to drum up what was corrected. Simply point out that in a final code review you spotted an error, and corrections to xxx variable was made. Overall associations/differences and conclusion remain unchanged. Give a short apology. And hope for the best.