Also - good news to the OP - if your son was baptized in the Trinatarian Formula than congratualations - your son is Catholic by baptism - he just has not has not had Eucharist and Confirmation yet. And if his condition is grave both can be conferred regardless of age - and if he should recover - even better - there are healing powers.
Baptism is a Sacrament that we share with the other Christian Churches - Marriage is the other. I am putting it simply - it is a bit more complicated but it should provide you some hope.
The sacramental bond of the unity of Christians
1271 Baptism constitutes the foundation of communion among all Christians, including those who are not yet in full communion with the Catholic Church: “For men who believe in Christ and have been properly baptized are put in some, though imperfect, communion with the Catholic Church. Justified by faith in Baptism, [they] are incorporated into Christ; they therefore have a right to be called Christians, and with good reason are accepted as brothers by the children of the Catholic Church.” “Baptism therefore constitutes the sacramental bond of unity existing among all who through it are reborn.”
An indelible spiritual mark . . .
1272 Incorporated into Christ by Baptism, the person baptized is configured to Christ. Baptism seals the Christian with the indelible spiritual mark (character) of his belonging to Christ. No sin can erase this mark, even if sin prevents Baptism from bearing the fruits of salvation. Given once for all, Baptism cannot be repeated.
1273 Incorporated into the Church by Baptism, the faithful have received the sacramental character that consecrates them for Christian religious worship. The baptismal seal enables and commits Christians to serve God by a vital participation in the holy liturgy of the Church and to exercise their baptismal priesthood by the witness of holy lives and practical charity.
1274 The Holy Spirit has marked us with the seal of the Lord (“Dominicus character”) “for the day of redemption.” “Baptism indeed is the seal of eternal life.” The faithful Christian who has “kept the seal” until the end, remaining faithful to the demands of his Baptism, will be able to depart this life “marked with the sign of faith,” with his baptismal faith, in expectation of the blessed vision of God - the consummation of faith - and in the hope of resurrection.
Well, you know more than we do - so take with a grain of salt what I just said before I get lynched - if you have any questions about his status see your Priest - he sounds conservative enough and a true protector of the Sacramentals.