Interesting post. I recently saw a documentary that you might find interesting. It is titled 'The Entity' and is from about 2002. It documents the experiences of people who appear to have suffered similar things to what you described about your boyfriend. Maybe you should watch it.
In short, it deals with two schools of thought about what may cause people to suffer this kind of 'sleep paralysis' as it is generally titled. The first is a closed-minded 'scientific' approach that tries to promote the theory that men can find 'rational' explanations for every question, and that such sleep paralysis must be a sort of mental condition.
The second school of thought is the more open-minded approach that indeed when people have such experiences in their sleep, it could be brought on by a mental condition, but could be just as likely a spiritual thing (ie. in the most extreme case, demonic). I'm not saying this to scare you, but just to let you know. And given that it is not only him, but a second person (yourself) who is sensing a dark presence, I think you need to stay open-minded about this.
My first piece of advise to you is to sincerely ask God to help you identify exactly what is causing your boyfriend to experience this. Put your trust in God, and not in men with their own agendas and biases, to make this clear to you.
In Hebrews 4:16 it says, 'Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need.' I think there is great value in this verse to all of us. I take it to mean that, while we all fall short of His standard, some of us still need to examine our own hearts, lifestyles, etc, and make adjustments to our ways before we can come to God and beg Him for his help. If we do this, and can approach Him in confidence, His infinite power is there to be called upon in time of need.
It's not for me to judge you, but are there elements of your life that you need to alter before you can approach Him in confidence? Sometimes there are several things, sometimes only one thing can be the hindrance. I'm not saying you have any such hindrance at all. Only God and you can know that.
Anyway, in summary, I suggest you find and watch the doco I mentioned, while earnestly praying to The Lord not only for true understanding of the problem, but a solution. He wants to help, and He can do anything He wants, but it may well involve you making a substantial initial step, to get yourself into a position in which you may be able to really help your boyfriend.
This may well also involve going directly to Godly authorities, such as a priest, and being open about these terrors that are afflicting your boyfriend.
I will also pray to Him on your behalf.
Anyway, good luck with this. May the will of The Lord be done in your life.