I agree with balso. Even though your plan gets you to Oriente Station well in advance of needing to be at the airport three hours before your flight, I would be a wreck worrying about all of those connections. Yes, you could easily take a taxi from your lodging to the Porto train station and you shouldn't have any trouble getting a taxi or Uber from Oriente Station to the airport (about a km away). BUT, have you read about all the train strikes in Portugal? Some announced just a day or two in advance? Are you willing to risk not being able to get from Porto to Lisbon on the day you fly home?
We were just there last month. Flew into Lisbon on Wednesday, spent the night near the airport, then flew home on Thursday. There are two very nice hotels just a short walk from the airport in Lisbon; we chose Meliá Lisboa Aeroporto. We took Uber into the central city for walking around and having dinner on Wednesday, then just had the short walk (we chose Uber and gave him a good tip) on Thursday morning.