What is the ruling on imitating the Hanafi madhhab regarding the non-pillar status of Al-Fatiha, and reciting it with some errors? And is the prayer valid with an error in reciting Al-Fatiha, such as reciting "Ihdina" with a hamzat qat' (instead of hamzat wasl)?

"Ihdina al-sirat al-mustaqim" is read with a kasra on thel hamzat al-wasl when starting with it. Dropping it while moving the letter 'ha' does not alter the meaning and is considered a subtle mistake (lahn khafi) that does not invalidate the prayer or the recitation; rather, it is disliked (makrooh). Your prayer is valid, and there is no need to imitate the Hanafis regarding the Fatiha not being a pillar of prayer. It is permissible for a lay Muslim to follow any recognized school of thought, and we advise you to disregard obsessive whispers (waswas).