Just because the dynamics in your marriage seem to have worked out does not mean they would for most couples. In general, a mixed marriage for a devout Catholic will present daily challenges. For a tepid Catholic married to a Protestant, the differences would be less pronounced. In this case, we have a devout Catholic and a devout Protestant who we perceived to be at odds. In later posts, some things were clarified. There is always hope for the OP staying with his girlfriend. But most people responding figure it’s a lot of work to reconcile religious differences.
A Catholic would have no reason to get up on a Sunday to go to his wife’s service if he had gone to Mass on the Saturday. If there are very small children, the Catholic could stay home with them and the spouse could go to her service. It doesn’t work the other way around because the Eucharist is not just symbolic for Catholics. It is an obligation which, once filled, requires attendance at no other service. In addition, you want your children raised Catholic and usually pledge to do so. The kids should really only go to one Mass each weekend.
Well some would say, how about the Protestant spouse wanting her husband standing and supporting her in her faith? Exactly. But it’s not easy for a Catholic husband to do that when he knows all the gaps in her knowledge cannot be filled due to her flawed view of things often combined with stubbornness. A devout Catholic knows the fullness of truth can only be found in the Catholic faith.