The mattress and its interior become tahir when it is soaked with rainwater while it is raining. Removing the water from it through pressing or squeezing is not required for it to become tahir, nor is it necessary to repeat the process.
The permanent marriage of a virgin is invalid without the permission of her father or paternal grandfather even if she has been raped. If she did not know this ruling, the sexual relationship without the mentioned permission is not considered as adultery. Since she comes to know of it, they should separate from each other and do not consider themselves as a married couple. They can get married in the religiously right way, by seeking the consent of the guardian.
The marriage is void in the said case since it is prohibited for a Muslim woman to marry a non-Muslim man. If she knew that her marriage was invalid, then the child is not considered tahir. If she was unaware of the invalidity of her marriage, then the child is considered tahir.