If the worshipper's dominant impression is that he is in the last raka'ah and he performs the tasleem, is he then required to recall the number of raka'at and what he recited in them after the prayer? And does he act upon his dominant impression if he doubts the recitation of Al-Fatiha in some of the raka'at, and does he add an extra raka'ah as a precaution?

You are afflicted with excessive doubt in your prayer. Do not pay attention to this doubt, and proceed with your prayer, building upon the larger number. So, if you doubt whether you prayed three or four (rak'ahs), make it four. If you doubt whether you prostrated two times or one time, make it two. Do not think or try to remember the surahs you recited after finishing the prayer; completely ignore this matter. Do not repeat the prayer, no matter how much you doubt its validity or completeness, for doubt after completing an act of worship has no effect.