Is it permissible for the Imam to recite Surat Al-Fatiha and long Surahs with the intention of completing the Qur’an in every Raka’ah of Taraweeh, then recite Surat Al-Ikhlas, and is this latter action not considered an innovation (Bid’ah)?

The Imam's concluding his recitation in prayer with Surat Al-Ikhlas after Al-Fatiha and the surah that follows it is not an innovation (bid'ah). This was done during the time of the Prophet, peace and blessings be upon him, and he approved of it. It is stated in the Two Sahihs (Bukhari and Muslim) that the Prophet, peace and blessings be upon him, sent a man who used to lead his companions in prayer, concluding with "Qul Huwa Allahu Ahad" (Say: He is Allah, the One). The Prophet, peace and blessings be upon him, informed him that Allah loves him.

In Sahih Al-Bukhari, there was a man from the Ansar who used to lead them in prayer. Whenever he began a surah, he would start with "Qul Huwa Allahu Ahad" and then recite another surah with it. The Prophet, peace and blessings be upon him, informed him that his love for Surat Al-Ikhlas had admitted him to Paradise.