Baptism renders people subject to the Roman Pontiff. He would cease to be a member once he ceased to profess the Catholic Faith or professed something other than the Catholic Faith.
Agreed.
You can't lose the faith until you consciously reject a part of it. A validly baptized person, with a protestant baptizer and protestant parents is Catholic until he rejects some aspect of the faith.
There is BOB/D and there is a Confession of desire. And even a spiritual Communion or Communion of desire in a manner of speaking. Of course none of the above take the place of the real sacraments and those who refuse to avail themselves of them despite being aware of their necessity will not be saved.
This is why there are "two sets of rules" for the those below the age of reason and those above and for those inculpable ignorant who have all the other prerequisites and those who are not. God judges the heart. We left the Mosiac law, where people go through the motions, doting the i's and crossing their t's while leaving their heart behind, some time ago.
God can sanctify the soul apart from water. He does not damn or save unjustly. He is perfectly Just (and Merciful).