N.B.
Sorry..but JMO...I do home daycare and can not imagine 3 year olds in cribs. All of mine are potty trained by that age so crib sleeping is definately out. Almost all of my kids in my experience are in a bed of some sort (mattress on floor usually) by age 2 to 2.5 LATEST. Often this is to accomdate potty training as well.
I would advise as others said, to not go backwards and certainly to not start the habit of them sleeping in your bedroom if you can avoid that. Eventually he will sleep in a reasonable amount of time. It might not be IN the toddler bed? It might be in a "nest" of blankets on the floor. Most parents I know just end of ditching the toddler bed if it fails and putting a twin mattress on the floor.
Always completely, totally child proof the room. Almost clear it out. Anchor dressers to the wall...put them in the closet if you can and make the closet child safe (not able to be opened) for safety. Makee only a few quiet toys avaialable, and a safe nightlight (plus covers in elsewhere, etc). The room becomes like a giant crib I guess.
Then let them do what they will. If its cry..if its look at the 3 books you left out with the stuffed lovey and a few blankets, by the light of a nightlight, so be it. Eventually they will get bored and sleepy and crash somewhere in there.
I have a daycare girl who will be 2 in June. She started a screaming fest a few months ago when put to bed. Refusing the crib. After a week or 2 of that, they put a twin mattress on the floor, did the room as I described (but ehr crib was still in there....they hoped she would go back to it), and shut the door at night (she was used to the door closed..and they had a little video monitor).
She screamed everynight for as much as an hour. It slowly receded, but she slept evey night by the door with her little fingers under the door, peeking out to the other side. It was a battle of wills, nothing else.
She sleeps just fine now, on the twin mattress and is asleep in a few minutes.
Best wishes!