I'd be careful with the child-proof knobs. We used to have one of the front door try and prevent the running (my boy was and is still a wanderer and runner)... all it took was one good whack one day on accident and it popped off. He hit it out of anger with a toy truck and the thing popped right off... after that he learned all he had to do was hit it hard enough and off it went. We were living in military housing at the time and were not allowed to drill into the door or door frame to install a latch or chain so it got very complicated after that. We finally convinced them to install a chain on the doors after a lot of begging and pleading. This was pre-diagnosis, we got a lot of "sounds like you need to keep a better eye on your kids, then!" from them... sadly, a child fell out of the second story window of one of the houses because of the lack of safety hardware installed/included with the houses, and after that they were more willing to listen to parents concerns about children getting out of the houses.

Child proof as many things as possible.
Is it a fear of him getting outside or just into things? A toddler bed is a very awesome step forward, don't hold him back. Work around it. $tree sells little alarm sets you can put on everything. The second the two parts aren't touching it squeals loud. You can put one on his bedroom door. You could put him to bed a little later or if it's constantly at a certain time set an alarm so you wake up and lay with him on the couch In the morning.

Baby gate...it's what I have for my 3 year old. This way I can keep the door open, but he can't get out at night.

I have a child proof knob. My daughter can't get out of her room. She sleeps with her twin sister in a toddler bed.

My son is 2.5 and so far still in his crib. I just caught him trying to get a leg over the railing the other day lol! He's pretty short so I wasn't too concerned until now. I think you have to keep your kid safe so if putting a gate at his room door is what will do the trick then there's no judgement there. I tried doing the toddler bed a few months ago and he wouldn't sleep, just wander his room. I had a gate up but I would guess the older they get the more likely they'll figure out how to get over the gate so yes, taller is better depending on age. I think as long as you're not closing the door on them (keeping them shut in their room alone) that a gate is fine. Jut keep your door open to hear and it should all be fine :)