You are undoubtedly aware that you are still a baptized Catholic and can return to the Catholic Church with all your gifts!
God bless.
Those marks of Baptism, Confirmation do not leave your soul. They are still there, even if you are an inactive Catholic.
I wonder if the FSSP or other apostolate would do the Sacrament of Confirmation entirely using the Liturgy of 1962. Or maybe this is their normal procedure.