I used the cry it out method at age 6 months for both my kids - we followed the book, Healthy Sleep Habits, Happy Child by Marc Weissbluth. It worked wonders, and my daughter only cried for 30 minutes. Your nurse & doctor didn't lie, this method works, but I will tell you, it is torture hearing the cries and not going in. I cried myself when while my husband and I were doing it. We only had to do it 2 nights before my daughter slept like an angel all night, so it is successful. The second night, she only cried for 10 minutes. My son was harder, but after 3-4 nights, he was fine. It may take you a little longer, since he's older, but it is worth a shot. If you're diligent about leaving him alone - I promise you and he will be ok after several days. I always felt that when you "go back in to reassure" made things worse for the child, and prolonged the crying. We didn't do that after the first night with my daughter.
Unfortunately your son is in a bad habit of sleeping with you in the chair, and you have to be the one to break it - he won't by himself. Since your son is almost a year, have you thought about a toddler bed - one that is close to the floor? Or even taking your crib mattress out of the crib and placing it on the floor - buy some "big boy sheets" to entice him. I know it's a bit early, but maybe he's ready.
By the way - benadryl can have the opposite effect on kids. When I have to give it to mine for allergies, they get hyped up. So don't count on that being an option.
I feel your pain and know you must be thoroughly exhausted. I know the cry it out option is tough, but with my experience, it does work because it teaches self soothing. My thoughts are with you. Good luck!