Yes, in a sense, they are still members. If they lost their membership 100%, then they would have to be re-baptized.
Not according to Msgr. Fenton ... who doesn't believe in the concept of an imperfect membership. I actually believe that it's possible, and could be used as a Catholic explanation for BoD. I had a big argument with LoT about this very subject. Fenton rejected the notion of imperfect membership held by some theologians, but I felt that he was wrong. At least with that you don't have to come up with an ecclesiology that allows the salvation of catechumens that results in this ridiculous idea of an invisible union with a visible body. He says that you can be within the Church without being part of it ... with the only visualization being not unlike an undigested piece of food inside the stomach. So I call that "undigested hamburger ecclesiology".
BUT ... generally speaking, according to St. Robert Bellarmine and others, heretic, apostates, and schismatics are NOT members of the Church. It's not unlike if someone cut off your hand. By virtue of the DNA, it still retains the identifying marker of having once been part of the body, but it's no longer part of the body. Similarly, the baptismal character of such a one indicates that the person USED to be part of the body, even though it no longer is (as taught by St. Thomas). So just like with the DNA markers of a severed limb. It's not just a dead member, but has actually been removed from the unity of the body. Now, if part of your body rots of gangrene or something, it's a dead member, but still a part of the body. Hair and nails, for instance, consist of dead cells, but they are part of the body. That's like Catholics who are not in a state of grace.