[ClumsyPilot]

Is he really in any risk of losing his job? I do not see how either your or OP came to conclusion.

I have met people who were under impression they were performing poorly, but actually they were doing great work. They just were disinterested in the job, which is a different issue.

[read_if_gay_]

The point is OP won't know if he it at risk, and yes Imposter Syndrome exists, so it's true that we don't know whether he really is at risk or not. But having kids still raises the stakes a lot.