Nearly all religions forbids intermarriage. But in case of Jews and Gentiles, the problem is not only the different beliefs, but also the different souls. A Noahide is not of different beliefs from a Jew. They keep the same Torah, though Torah itself orders different mitzvot for them. However a Noahide is also forbidden to marry a Jew. If a Gentile marries a Jew, it's not only the Jew who is harmed, the Gentile also. A Gentile needs a Gentile mate.
You can get a civil "marriage" certificate but you are not married. That certificate would be nothing more than a piece of paper with a lie written on it, so you and your "wife" will be still single and just have sex outside marriage.
And if you have children with a Jewess, they will be 100% Jewish and I suppose they will be only her children, not yours.
Now, regarding beliefs, why are you Catholic and why wouldn't abandon your faith? I suppose that's because you truly believe that you need Jesus and the Church to save your soul. Then why would you allow your children to be brought up as Jews? According to YOUR beliefs, your children would not have eternal life. And if you think a person can have eternal life without Jesus, just believing in Hashem, the Holy One, as the Torah commands, why don't you accept Torah now, and do what Torah tells to Gentiles? (Torah has a way for Gentiles, that is The Seven Noahide Laws). Why dont you become a Noahide? However, as I have written above, even being a Noahide, you can't marry a Jew. That's not a prohibition, it's a natural law. Marriage doesn't exist unless both are Jews, or both are Gentiles.