Max Watters powered the Tykes ahead in the first half before Shamir Fenelon equalised in style for the visitors.
Horsham stunned Oakwell when James Hammond thumped home a penalty but Fabio Jalo’s sensational effort saw Barnsley level on the stroke of half-time.
Mael De Gevigney headed the Tykes in front just after the hour mark, before second half substitute Tom Richards tapped home with nine minutes remaining to secure a famous replay for the Hornets.
The two sides will meet again at the Camping World Community Stadium on Tuesday, November 14.
Di Paola said: “I thought the boys were absolutely phenomenal. It was just an incredible performance. I don’t think there was anyone without cramp!
“To put in that performance away from home against a side as good as them, with a lot of their starting XI out there and some of the subs they bought on, was just incredible.
“I’m so pleased. There’s been a bit of controversy around the FA stuff and there’s been some issues here. I notice there isn’t any police, which is quite ironic considering that was the reason the game was supposedly moved.
“It’s just so pleasing we can bring them back to our place and we can bring the town out and be allowed to watch our supporters see us in such a high-profile game.
“It’s a massive credit to all of our players. The subs came on and changed the game.
“We’ve worked so hard this week, mainly on the tactics board because we haven’t had time to get out and do bits.
“I didn’t feel like we parked the bus. I felt we had an attacking threat. It’s so pleasing that we didn’t come here and roll over and accept waves of attack.”
The Hornets’ Cup clash at Oakwell was moved to 7.45pm this evening [Friday, November 3] – having been switched from Saturday following talks with local emergency services.
The Horsham boss felt ‘justice had been done’ after the furore – but questioned the lack of police presence in a fixture which had been moved after consultation with the local force.
Barnsley head coach Neill Collins praises dauntless Horsham after never-say-die performance at Oakwell
Di Paola said: “I do feel justice has been done. I never understood the decision in the first place. As I said, I haven’t seen a single police officer anywhere in the vicinity tonight, which makes me think that [the decision to move the tie due to policing] was never the case.
“If they were concerned about policing, and they needed police to police the game, why has it been stewarded?
“You always have to be a bit polite about these things, but it was a huge inconvenience. We travelled up last night in rush hour, the boys have had to take time off work.
“Sometimes in football it balances out. For us to have our moment here like that, maybe it was for the best it was on a Friday night!”
Di Paola also hailed the impact of his substitutes in the draw at Oakwell. Second half replacements Lucas Rodrigues and Richards combined to net the Hornets’ equaliser at the death – and force a potentially lucrative replay at the Camping World Community Stadium.
Di Paola added: “We changed to a 4-4-2 and went for it. Lucas and Kadell Daniel came on and it gave us a bit of thrust for just a short period.
“At one stage we talked about bringing on all five subs at the same time to have almost a complete reset because we knew we’d get leggy.
“You kind of hope you can have a little moment in the game, but I felt like we had to do it early.
“The boys were saying we needed to stay in our shape because we’re doing alright, but I didn’t feel we had the legs to grab one in the last minute. We had to make that adjustment with 20, 25 minutes to go because I don’t think we would have had the legs to do it late on.
“You always know in football you’re going to get an opportunity and you have to take it. In that moment, they switched off slightly and we got round the back of them. I think there were three of our players in the box, which is great at that stage of the game.”