A.S.
My husband is major sleepwalker, with occurrences that sometimes happen a few times a week. He has turned violent and attacks things if he thinks there is an 'intruder', including me, so we have to remove things from our room, like lamps, picture frames... and we use lots of nightlights to help. Keeping a safe environment for them is very important.
You have to learn to talk to them. Forcing them to wake up, grabbing at them and overreacting can make it much worse, as they will be confused and scared and act out.
I just gently talk my husband out of it, he sometimes argues back, but I reason with him, keep a safe distance and he realizes he was asleep and goes back to bed. He sometimes remembers bits and pieces of it.
Stress, sickness, exhaustion and some medicines makes sleepwalking much worse.
If he is screaming and his eyes are closed, sweating, with an increased heart rate, I would say that is closer to night terrors, though night terrors typically happen with younger children. Talk to his Dr. about it. Here is some advice on dealing with night terrors:
It is a 3 page article with lots of help:
http://children.webmd.com/guide/night-terrors
Here is one on sleepwalking:
http://www.stanford.edu/~dement/slpwalking.html
http://www.sleepeducation.com/Disorder.aspx?id=14