At around 6 weeks most babies hit a growth spurt, so he's almost certainly trying to increase your milk supply by feeding more frequently - even if he doesn't empty, he will be stimulating you by sucking even a few sucks.

I'm not sure when it's "ok" to stop feeding at night. In the interests of sustaining your milk supply it's better to let the baby be in control because he intuitively knows how to work your boobs. My DD fed at midnight and 5am until she was 7 months old, and during growth spurts she often came at 3am too.

Bx