ohh, it's tough, but you know you love him and just keep re-inofrcing that as you leave, that you love him soo much that you want him to get a good nights sleep so he can have more fun tomorrow. I fully believe you've gone through the worst of it. Don't give up now.
Also, does his cot convert, or can you get him a bigger boy bed? Maybe atttaching something special as a reward for going to bed and going to sleep like a big boy would be something positive. We felt our kids were rolling into crip sides and waking themselves up so we moved them to big beds, with removeable side rails at age 1. I don't know that it was any better, but it allowed us to get rid of the crib.