1) If an ACA has been nominated, such that the pilot - for whatever reason - is unable to successfully go around below said ACA, then this should take into account the configuration at the time. Once below the nominated ACA then flap setting becomes less relevant, since the pilot has already decided that a go around is less likely to result in success. Many light twins will lose some height while transitioning from a stable approach to an asymmetric climb.
2) The autopilots fitted to all generations of DA42 (KAP140 or GFC700) are specifically prohibited from use in single engine scenarios in the POH.
Glad to hear your ratings were endorsed post-flight. Changing the result based on either of the debrief points mentioned would have been highly risky!