Catholics still consider baptism a holy sacrament, right? If that's still the case, then you would consider our baptisms to be invalid. That's what you told me before, re the validity of Presbyterian sacraments...
Well, Alex, since, e.g., Prebyterians reject apostolic succession, reject the idea of the priesthood per se, and reject transubstantiation or anything close to it, there's really not much chance of a Presbyterian Eucharist being a valid Catholic sacrament. Sacramental validity requires a valid minister, valid matter ..., valid "form" (the words that are said, and valid intent (the intent to do what the Catholic church does). Unless your Presbyterian minister is a former Catholic or Orthodox (or perhaps Anglican) priest, he's not a validly ordained minister. He probably doesn't have a valid intent, either.
My husband, a former Presbyterian, was not rebaptized when he entered the Catholic Church.
Just my two cents.
Baptism doesn't require Holy Orders, so the "valid minister" of baptism is anyone at all. (A Catholic layman qualifies. A Presbyterian minister qualifies. In fact, there's a medieval council somewhere that decreed that anyone, "even a Jew" (their words) can validly baptize.)
The valid form requires the invocation of the Trinity ("Father, Son, and Holy Spirit", not "Creator, Redeemer, and Sanctifier" or drivel like that). Most conservative Protestants qualify there, too.
Valid matter involves water. There's been some questions raised about Protestants who baptize by sprinkling, but pouring and immersion are certainly okay. (Catholics do both.)
The intent can be a problem, but theologians generally agree that "intent" means "the intent to 'do what the Church does,' that is, to baptize in the name of the Trinity".
Protestant Eucharists, confirmations, ordinations, etc. are not recognized as valid because they require a valid minister. Protestant marriages are valid unless one or the other party is a Catholic marrying without a dispensation.