Minimum requirements for Taslim after prayer

Assalamu ‘Alaykum,

when I recently reached the Taslim at the end of my prayer, intending to use the wording “Assalamu ‘alaykum wa rahmatullah”, but a mistake occured in “warahmatullah” whereby the ‘r’ was most likely missing. I read, that the opinion of the respected scholer Al-Nawawi is that saying only “Assalamu ‘alaykum” would be sufficient. Although I could not find confirmation for this, I followed this anyway.

Furthermore, since “warahmatullah” was mispronounced, it was no longer part of the Taslim. As such, when I finished saying “Assalamu Äalaykum” my head had not yet completed the full rotation of approximately 90°, as is indicated in one or more ahadith.

Thus my two questions are:
Is the saying only “Assalamu ‘alaykum” sufficient?
Do the ahadith concerning the Taslim imply that it is fard or sunnah to turn the head to the sides?