I've done this trip in reverse: Renfe train from Santiago to Vigo, and then Vigo to Porto via CP, or Comboios de Portugal. It worked our fine, although we did have to wait a few hours in the Vigo station to pick up the Portuguese train. You'd have to examine the schedules to see what kind of connection you can work out going the other direction. I agree with Trecile that bus is simpler and more direct, although you mentioned you don't do well on buses.
On the other hand, as you observed, rail strikes are a problem in Portugal right now -- everybody in public service is doing intermittent strikes: railroad personnel, doctors, nurses and teachers. One thing you can do is download the CP app and monitor the situation. The app will give you warning if a strike is going to hit when you're planning to travel.