You need to discuss all these things thoroughly with Mr. Protestant before you get serious about him:
Is he okay with you continuing to practice your faith? Is he respectful of it?
Does he practice his? Is he open to maybe joining with you to practice yours? Would he perhaps convert?
How does his family feel about this? Are his parents okay with it? Do they accept you and your faith? Will you be expected to go to Protestant services with them on family visits? Will they accommodate your desire to go to a Catholic Mass? Do they make upsetting remarks or jokes about Catholics?
How about the kids? Is Protestant dad okay with them being raised Catholic? Are grandparents going to interfere?
Does Mr. Protestant agree to marry you in the Catholic church? Is he willing to jump through the required pre-Cana hoops?
Does he accept the Church teachings on sex, porn, contraception, and marriage in general? Does he understand that for a Catholic, marriage is forever, divorce doesn’t end anything, and annulment is not guaranteed, so this is a big step for you?
If all of this stuff is not a problem, or if he agrees to convert, then he is “marriage material”.
My mother married a Protestant who converted. They were married about 27 years till he died. It was a happy marriage. She didn’t want to date or marry anyone else after he died.
I married a Protestant. He is a good man and his family is nice to me. A couple of them are also Catholics as one guy converted to marry his wife. Some of the grandparents were also Catholic. Apart from an occasional Catholic joke (they lived in a heavily Catholic area so were used to having Catholics around), no problems. We have been married 23 years. I am working on getting him to convert now that his parents are deceased.