I understand very well what you are saying. I know how them catholics are, I grew up as one and was supposed to be a minister, like one of my great uncles, two of my great aunts were nuns. We were pretty catholic, I can tell you this.
Here comes this catholic bloke from Germany, and wants to marry the daughter of a family that was as proud as the dickens to be of pure British blood. When my future wife told my future father in law that we want to get married, his only answer was "at least he is not a Martian". This family scenario I had, when I came out (we were divorced, but I was still part of the family), and everybody of that family congratulated me and is part of my support group (including my niece, who is a Pastor).
It is very often those who you expect would reject you, who accept you the most. I know, your situation is different than mine, and only you are the one, who has to face it, but if we can give you any kind of support, please let us know, we listen!
Hugs
Linde