Is the inability to distinguish the recitation of Al-Fatiha and the pronunciation of words as connected, such as (waladaleen) instead of (wala ad-daleen) or (al-sirat limustaqeem) instead of (al-sirat al-mustaqeem), considered due to waswasah (whispers from Satan) and thus does not necessitate re-recitation?

You must recite Al-Fatiha, and as long as you have recited it, your feeling that you are mispronouncing words does not matter, because this feeling stems from waswasa (whispers from Satan). The best cure for waswasa is to ignore it and pay no attention to it, and for a person to treat themselves as being correct and having fulfilled their obligation. If they do that, the waswasa will disappear.