Thinking of trying CIO even though I am against it?

I had a daughter who sounds identical to your son. I was NOT for CIO at all. One day though I was so tired I put her in her crib crying and let her cry for a few minutes. I would come in and check on her to make sure she knew I was in there and then would leave again. It was exhausting but after a few times of doing this she fell asleep from exhaustion. It took a few days for her to realize when night time was. To be completely honest if you keep letting him do it he will. Make sure you put him to bed at the same time and keep repeating it. Do not take him out of his crib. Just go in the room, check on him, and leave.