No, the portals and the other worlds are for mortal sinners. They get there via the lake of fire, which is not the case for sinners going to purgatory. Granted, I could just wave my magical fiction wand and make it so, but it seems very clean at present in terms of a reader wrapping their minds around the story, especially a Catholic reader. The more I deviate, the harder it gets for them, and the less they're likely to like the story, imo.
Technically, one doesn't get a glorified body until after the Second Coming, so I guess you're just a disembodied soul waiting in Heaven for the Second Coming. Eve, if you recall, does get her glorified body, so she could be at the center of events to keep an eye on Adam/Connor, although that part of her mission doesn't begin until book 2.
Antonio will be the example of what purgatory is like in this story. It's not truly Catholic, but then not much is known about purgatory. I figure if you want absolution from a priest, you usually need to do some penance. If Antonio wants out of purgatory, he needs to make things right with Romano, which includes telling Romano the truth (that Antonio had already gone to confession prior to being hit by the truck, but he allowed Romano to think he died in a state of mortal sin). I'll treat what he did to Romano as a venial sin.
Antonio will continue to travel with the group like in the first draft, but he also needs to do some good works before he gets out of purgatory. If you recall, he "cured" Connor of the spiritual poison by figuring out the solution and dunking Connor in the Sea of Galilee. Naturally, Connor wasn't actually sick, but Antonio didn't know that. Still, I'll probably make that the last thing he needs to do to complete purgatory, even though Antonio won't know it right away.
So, for some reason, he remains with the group throughout the entire trip. Eventually, he'll get a chance to ask Phanuel what else to do to complete purgatory. He's told he already did complete it, and he may go to Heaven whenever he wishes. But he decides to do a few more good works by staying with Romano to oppose the efforts of the Unholy Trinity. My other option is to simply keep Antonio in the story, while he thinks he's still in purgatory, whereas in reality he cares too much about Romano and Connor that God knew he'd rather stay in purgatory long enough to finish his life's work. He would then find out at the end of book 3 that that's the real reason he's still on Earth.
One thing I'd like to include, though, is the idea that Antonio becomes more and more holy as he does more good works. It's a transformation that would happen automatically. It slowly purges him of sin, so he can go to Heaven, which definitely is Catholic. I just have to be careful that his holiness doesn't ruin him as an interesting character. I figure he can still say sarcastic things without them being sins.
Did I answer your question? :-)