Personally I don't set alarms for WBTB, I wake up naturally multiple times during the night. I don't like to wake up too much when I do my WBTB's though, I tend to lay still, remember my dream clearly then write it down in my dream journal. I might have a sip of water but then I'll just lay back down and still be tired enough to go to sleep.

It's really about finding what works for you, some people like to get up and do a lot of things, but it sounds like you need to stay more relaxed and sleepy