Is frequent passing of gas, especially during prayer, with an inability to distinguish whether gas was actually passed during prostration due to gas buildup, considered a case of continuous flatulence (sils al-reeh) or not? And if not, what is the remedy for this condition?

If you experience what you mentioned in the question with every ablution for prayer, then perform ablution for each prayer after its time has begun and pray the obligatory (fard) prayer and whatever voluntary (nafl) prayers you wish. This is because it is what you are capable of, and Allah does not burden a soul beyond its capacity. In this case, you are considered like one who suffers from incontinence (sahib al-sals). However, if these are merely delusions, then ignore them and turn away from them, for there is no better cure for obsessive whisperings (waswas) than to disregard them.