I want to start out by saying that Porn a problem whether you are D.I.D. or not but even more so if you are as the Host may hate porn, but an alter may love it or be addicted to to it if he/she host is addicted the problem could be D.I.D. related but the Host needs to be set free first see recoverthesword.
I hope you can see the problem can be very bad as it is a problem big even if you are falsely persuaded that porn is harmless to an adult. In D.I.D. there may be children present even if it is unknown at the time. Such as in this authors case the children were effected as well as some of the other adult alters when the Host was addicted when the HOST is free they can still be effected by the alters conduct. Whew what problem this can be for example when the Host was addicted to spanking porn the man hater was made even more hateful while the woman hater was fueled by the abuse of the women.
I am convinced once the host is free the alters will fall in line with a little pressure. Use the other alters to use positive peer pressure, and ask the Lord of Glory to convict the alter. It is a war, if they are not cooperating but you must not give in and let them have their own way. Any time they download porn delete, it if they buy it destroy it. Will this make them mad? You bet! but it is the Lord you are pleasing not the flesh. just because they are alters don't let them do things you would not do. As you know by now the best discipline and painful it is to an alter is not giving them any "out time" for a while. The Lord did this to mine before I knew about the out time and lack there of being punishment to them, good discipline rather as it is not retribution but correction. He ,the Lord, made one of mine unable to come out for two whole weeks and this was a very out front one. This was highly effective at curbing behaviour.
Get an accountability program in place as soon as possible. This is something I did not do until I thought I was integrated I thought what the use. What the use? Looking back now I wonder how much sooner the alters would have been delivered of that and how much sooner that fight with. Get accountability or stay in the prison of porn at least your alters that is. Make sure to see recoverthesword