Looking with interest as we are at wits end with our 2.4 month olds sudden refusal to go to bed. I empathize OP. DH and I reverted to rocking him to sleep when we made the switch to toddler bed because he just wouldn't stay in it and self-settle the way he would in his crib. We are trying to move away from that but haven't had much success. Perhaps we can compare notes...what's working and what's not.....
We tried sitting in his room...this was taking a ridiculous amount of time which we do not always have with more than one child.
we tried the whole supernanny stay-in-bed technique but he just gets hyper - giggling and laughing and launching himself off the bed in glee. we tried that technique with us in the doorway out of sight, then in the doorway in sight and the in the room with our backs turned to him but really to no avail.
Then we decided he needed a longer whind down time so tried reading to him in his bed (he wouldn't stay still), now are trying to read to him while in a chair and doing a bit of rocking but not to sleep (jury out, but from what I can hear of DHs efforts tonight so far, not going well).
weve tried the gate in front of his door thing but one of two things happen....either he becomes hysterical to the point where he cannot calm down and I hedge on my parenting principals or he plays in his room absolutely no closer to sleeping than when we started.
sorry, none of that specifically helps you, but perhaps the ideas just need tweaking from some wise Mner.
I hope you get some guidance here OP that I can sponge off of because it is exhausting and very trying.