porto airport to campanha train station?

It's a bit over a half hour ride on the metro system.. Departures every ten minutes or so. Assuming you can't hop on as the door is closing, best case, that's forty-five minutes.

You've eighty-five minutes total, so forty left to clear the plane, get baggage, hit customs and immigration, find the tram. At the other end you've got to find the train and maybe get a ticket.

Nope.

I was afraid of that. Would taking a taxi make any difference? Will I have to clear customs if we are flying to Porto from Paris and not the US?

No C&I since it's intra-Schengen. No checked junk would help, also. Then, I'm guessing you'd be down to forty-five plus fifteen plus ten - - fifteen theoretical minutes of slop at absolute best wouldn't ring my bell.

I've never driven exactly from the station to exactly to the terminal but I don't think I could make it in thirty minutes. Probably no advantage to a taxi.