K.M.
My husband and I were vehemently opposed to CIO. We thought it was cruel and that any parents who did it were selfish and more concerned about themselves, not the baby. Babies cry to communicate, right?
Then we had our second child... HORRIBLE sleeper! It was EXACTLY what you have described with your son! But being stubborn know-it-alls, my husband and I continued to believe that CIO was not right for our family.
That was until he was a year old. Enough already.
We "Ferberized" him. It was a week of hell. But we did it and it was hard on EVERYONE. We all hated each other. Our daughter was miserable, my husband and I were snippy with each other, but then one night, something really amazing happened: He went to sleep. And all was right with the world!
Bite the bullet. Take a week and prep everyone. Set ground rules so that you and your husband are on the same page and be consistent! Your little guy will be fine, it's just gonna be a bumpy ride! Go for it and good luck!
PS- Check your local library for the book. It's an easy read.