Has he had an accident recently? I've found with DD1 that if she has an accident she because hyper vigilant about going to the bathroom and gets up frequently at night. After a few days it goes back to normal.
Can you encourage him not to wake you? I know you said even his noise would wake you, happens to me too, but being woken up but still in bed is entirely different than having to get up. When we night trained DD1 (we needed to use the Malem alarm) that she was only to wake me up if her sheets were wet but if she was just using the bathroom she didn't need to wake me. It took a bit of reinforcement but she did stop waking me every time she went. While her turning the bathroom light on w/out closing the door is enough to wake me, I can easily fall back to sleep since I didn't have to get out of bed to assist her.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.