Hello, and thank you for this thread because it helped me a lot. I specially appreciate the reflexion that if complete understanding of catholic belief was needed, no baptism from non-catholic would be valid. I find this decisive. Actually this matches a reflexion I just had on Act 8,14-17 while searching a bible passage about confirmation*:
«Now when the apostles in Jerusalem heard that Samaria had received the word of God, they sent them Peter and John, who came down and prayed for them that they might receive the Holy Spirit. For He had not yet fallen upon any of them; they had simply been baptized in the name of the Lord Jesus. Then they began laying their hands on them, and they were receiving the Holy Spirit.»
I notice that it is said that they had been baptized in the name of the Lord Jesus, which could even bring doubt about the use of the trinitarian formula, though I know this is not the catholic interpretation in this case. Whatever, I find it nice we have this wonderfull sacrament of confirmation, which normally can only be given by bishops, and so it’s like make perfect the baptism with no doubt possible, and receive the holy spirit*!