Are Hindu children meant to serve their parents forever whether they like them or not?
Seemingly Yes.(See verse 2.235 given below for example)
Importance of Parents and Guru from Shastras:
Manu smriti 2.227. That trouble (and pain) which the parents undergo
on the birth of (their) children, cannot be compensated even in a
hundred years.
2.228. Let him always do what is agreeable to those (two) and always (what may please) his teacher; when those three are pleased, he
obtains all (those rewards which) austerities (yield).
2.230. For they are declared to be the three worlds, they the three (principal) orders, they the three Vedas, and they the three sacred
fires
2.232. He who neglects not those three, (even after he has become) a householder, will conquer the three worlds and, radiant in body like a
god, he will enjoy bliss in heaven.
2.235. As long as those three live, so long let him not (independently) perform any other (meritorious acts);let him always
serve them, rejoicing (to do what is) agreeable and beneficial (to
them).
Do children need parents' permission to live away from them?
Yes,once again.
Manu smriti 2.229. Obedience towards those three is declared to be the
best (form of) austerity; let him not perform other meritorious acts
without their permission.
2.236. He shall inform them of everything that with their consent he may perform in thought, word, or deed for the sake of the next
world.
What do scriptures say about parents doing such negative acts?
Manu smriti 9.290. For all incantations intended to destroy life, for magic rites with roots (practised by persons) not related (to him against whom
they are directed), and for various kinds of sorcery, a fine of two
hundred (panas) shall be inflicted.
So,apparently such acts of using black magic for harming others come under punishable offence.
What if parents are just bad apples, should children continue to serve their needs?
What do the shastras say?
Abandoning parents,Guru or even a son,without sufficient reasons,is condemned in Shastras.Here the key is without sufficient reasons.
Manu Smriti 3.157. He who forsakes his mother, his father, or a
teacher without a (sufficient) reason, he who has contracted an
alliance with outcasts either through the Veda or through a marriage..
commits a minor offence.
So,the purport probably is,if there are enough reasons,one can abandon such bad parents.
Take a look at what the Usana Smriti has to say in this regard:
There is no Deity equal to mother ; there is no Guru (elder) equal to
father ; there exists no return of their good offices. (35) One should
by deeds, thoughts and words do unto them what they like. Without
being commanded by them, one should not perform any religious rite,
excluding those which yield emancipation and the daily and obligatory
rites. [To serve the parents] is laid down as the cream of religion,
yielding delightful fruits in the next world. (36 37)
