It is permissible to get temporarily married and it is unlawful to have intercourse with a virgin except with the permission of her father or paternal grandfather, even if she is financially responsible for herself. If both of them are dead or cannot be reached to seek their permission then she is in charge of herself.
After choosing a certain Marja who is qualified to be followed and following him, you should continue following him, until it is proven to you via religious evidence that indicates that there is a more knowledgeable living Mujtahid than the current Mujtahid. It is not permissible to pick verdicts from another Marja just because it suits you.
There is no doubt that being ungrateful to one's parents (Uqooq) in any form is amongst the greatest prohibitions, and the committer of such a sin has been warned by Almighty Allah with the punishment in hellfire.