Hi Meredith,
We went through a very similar thing with our DS this summer. I think he's testing you, for sure. If it were me, I would stop "helping" him to lie down. If his issue is SA, then you can continue to sleep in the room, but when he wakes up - say "it's sleep time, lie down." and don't help him.
It's likely that he'll throw a fit if you don't "help" him lie down, but that's ok. He's just showing his frustration. Just stay in the room and stay on your "bed" and say things like "I know it's frustrating, but it's sleep time - lie down." He will eventually lie down and go to sleep. He might cry for a long time - but you have not left him - you are just letting him work it out, he is old enough to do that.
After you've got that sorted out, I would start moving your "bed" area away from his crib and into the hallway. With a kid his age, you can quickly get trapped into sleeping in his room for weeks and months. He's not going to like it, but just remember - you are not abandoning him - you are right there. You can talk to him and reassure him with your voice without leaving him to cry alone. I'd get started on that asap if I were you - my experience has been that the older they get the more "stubborn" they are in their protest ...
As for the weekend - you might *try* to let him sleep alone, it might be that the new/different place will be helpful in kind of "re-setting" his expectations that you will stay. But do be prepared to camp out in there if it doesn't work out.
Kate