We moved Tyler to the big boy bed when he was just a couple months older than your DS. We put a bunch of quiet toys in there at first to help him forget to be scared...books, some Thomas trains (if that's quiet play for your DS), stuffed animals, etc. The first couple of weeks, he would stay in there happily and play for up to 2 hrs, even though we'd made it clear that it was time for bed when we put him down. He didn't stay in his bed, but as long as he was happy, we let him be. Eventually he'd fall asleep on the floor, bed, wherever. He had a couple of weeks where he was sooooo tired because he wasn't getting near enough sleep, but it took 2-3 weeks max before the novelty of his quiet toys wore off and he started falling asleep faster. That's when we started to gradually take toys out of his room and now there's just a few books and stuffed animals. To this day, he'll still take awhile to fall asleep sometimes, and I could care less what he's doing in there as long as it isn't dangerous and he's happy. So you might consider just letting him be if he isn't calling for you...as a pp said, the novelty does wear off, and I kinda think it's a waste of energy to try and get an energetic toddler to lay down in bed and stay there. But that's just me.
Is the door closed? When he calls for you, could you try reassuring him from outside the door and only going in as an absolute last resort? If that doesn't work, some WI/WO like you've been doing sounds like the right thing.
The bed jumping would scare me for safety reasons, though. Is your LO's bed off the floor? You might think about just putting the mattress on the floor by itself so that if he jumps, it isn't dangerous and that's one less thing you have to deal with. The novelty will wear off! And yes, early wakings are common during a transition like this...he's overtired, but it will pass.
