Yes, Paul/Saul existed. I don't know what happened when he experienced his 'revelation'. Jerusalem to Damascus is about 270km, more than a week's walk or four days by horse (no idea about travelling times of donkeys or camels!) It would've been a tough trip, passing through regions where neither Romans nor Jews were popular. He and his party were probably tired, pissed off, and may not have eaten or slept well en route.
When I've imagined being in his party, I tend to think of him in a state of moral conflict: he may have been sympathising more and more with the Christians, trying and failing to square it with his successful career. If he went over to the other side, he'd lose everything he had worked for and put himself at risk of execution by his own soldiers.
He was travelling with those soldiers, but were any of them also sympathetic to Christians? Some may well have been: it was the cult of the day, spreading like wildfire - hence the urgent suppression campaign. I imagine Paul's party passing that long, dusty journey under tension, discussing the new faith cautiously while never daring to openly question their mission.
Two days out from Damascus, the desert sun rises once more and ... he has a panic attack? A seizure? A massive tantrum? Or maybe just passes out from fatigue. Any such thing is possible; we don't know his state of health at the time, only that he was engaged in a physically and emotionally taxing project. Perhaps he had dysentery and collapsed in a poonami (they wouldn't tell us that!)
People didn't have "stress-related" illness in those days and their understanding of medicine was 99% superstition. Everything that happened was an act of god. When the boss dramatically collapses, then comes round ranting about God's will and saying he "can't see", it's a guarantee that [a] this is the work of a great power, and [b] everyone feels that something mystical has happened to them personally.
I suspect his blindness was metaphorical. His inability to "see a way forward" may have led him to become literally unable to see, or he might just have said it so much that the others took it that way.
When Ananais got to him in Damascus, Paul's party hadn't eaten for three days. They were weak and would have been extremely susceptible to this kindly prophet turning up with food and drink. For Paul, without a doubt, it was the assurance he needed; he could see his way clearly.
A 2012 paper in the Journal of Neuropsychiatry and Clinical Neurosciences suggested that Paul’s conversion experience might be understood as involving psychogenic events. This occurring in the overall context of Paul’s other auditory and visual experiences that the authors propose may have been caused by mood disorder associated psychotic spectrum symptoms.