I have always been advised - make the plan and stick to it - however at 2am in the morning after toddler has been crying for 30mins - very hard

I would also suggest putting him in his own bed at the beginning of the night and sitting with him until dopey/asleep for a start, and then after a couple of nights, leaving earlier saying you will be back in a minute to check - and do check etc

I had the same issue when my DS was around that age with DD in my tum. we also ended up putting a spare cot mattress on the floor of our room and told him if he wanted to sleep in our room, he could sleep on that mattress. protest, then he slept on it, and then once out of our bed, back to his etc.

Good luck - it isn't easy when you are trying to get sleep yourself - especially if DH can't handle the crying in the night or won't get up - like mine too grrr.