Being a sunni means follow the sunnah, it doesnt mean exagerating in your deen. Theres no need to add durood in the recitation: The Prophet SAW said in the hadith recorded by At-Tirmithi and others: The invocation of my brother, “None has the right to be worshipped save You; Glory be to You, far removed are You from any imperfection; I have been amongst the wrong-doers,” ( translation of the Ayah you have given ) none who is experiencing difficulty employs it except that Allah SWT would relieve him of his difficulty. Pretty clear. Lets not make it murky