Is Watching Porn Haram?
Question

My husband has a high stress job and he says the only way he can relax is to engage in various sexual acts such as watching porn together or fantasizing about threesomes or having sex on Web camera with someone watching. I know all this is haram, we have a very good relationship otherwise but he pressures me for these things and I do not want to refuse him as it creates tension between us. I have tried talking and explaining patiently but this issue keeps coming up again and again. I would like to add that the only thing that makes me refuse is the fear of it being prohibited in Islam. I am not forced in any way by him. Just a sort of pressure and if I refuse he is kind of cold towards me. I am very worried and stressed about this. Please advise me on what I should do. And also tell me the punishment for these acts.
Praise be to Allah.Is Watching Porn Haram in Islam?
Watching pornographic websites and sexual activity is haram; it is a disease, not a remedy. The one who does that is afflicted and he should seek to remedy himself by repenting and giving it up, not by making up excuses for himself. 
All sinners make up excuses for themselves. The one who drinks alcohol or takes drugs or commits adultery – they all claim that they are under pressure and that they cannot escape it except by doing something haram. 
In fact, these haram things only add to their worries and stress. One of the punishments of sin is feelings of stress and alienation, and darkness on the face and in the heart. The further away a person is from his Lord and the more he is indulging in sins, the further away the means of attaining happiness and peace of mind are from him, as Allah, may He be exalted, says (interpretation of the meaning):
“But whosoever turns away from My Reminder (i.e. neither believes in this Quran nor acts on its orders, etc.) verily, for him is a life of hardship.” [Ta-Ha 20:124]
As for the people of faith and obedience, Allah, may He be exalted, says concerning them (interpretation of the meaning):
“Whoever works righteousness, whether male or female, while he (or she) is a true believer (of Islamic Monotheism) verily, to him We will give a good life (in this world with respect, contentment and lawful provision), and We shall pay them certainly a reward in proportion to the best of what they used to do (i.e. Paradise in the Hereafter).” [an-Nahl 16:97] 
Husband is addicted to porn; what should I do?
What you have to do is advise your husband to keep away from these haram things , and tell him about beneficial remedies to treat stress and anxiety , one of the greatest of which is reading the Quran, which is the means of bringing relief and peace to the heart. Please see the answers to questions no. 21677  and 30901 . 
Guidelines to intimacy in Islam
It is permissible for the husband to enjoy his wife however he wants , so long as he avoids intercourse at the time of menses and in the anus. 
There are different ways of enjoying intimacy that are not forbidden in Islam, but they are off-putting to people of good taste and sound natures; however they are permissible if the wife agrees to them. 
If your husband calls you to do something haram, you have to refuse and not be a party to sin and disobedience. If he calls you to do something permissible that you find off-putting and distasteful, then it is up to you whether you accept or refuse. If you decide to go along with it because you are afraid he will lose interest in you, you may do so, but it is better for you to fulfill his desires in proper ways that do not make either of you feel put off. 
And Allah knows best.