I gave up a pack a day smoking 20 years ago when I developed early signs of COPD. I then went on to contract athsma a few years later, then UC in '06. I've got the asthma under control but have never been able to reach anthing near remission with UC. A few years ago I tried the nicotine patches for a couple of weeks to no avail. If I recall correctly, I started with the lower dose (10mg?) and they gave me weird nightmares. When I kicked up to the higher (20mg?) patches, I got the most horrible vivid screaming nightmares where I would wake up in cold sweats. I promptly stopped them after a few nights and not only for my wifes sake I might add.
So nicotine itself did nada for me. As Garylouis said, I think it maybe a combo of nic and the many other chemicals that go into smokes, although I'm not sure about CO. I'm (semi-retired) in the gas appliance home safety inspection authority and I'm regularly 'exposed' to CO. Carbon Monoxide is more to be feared and respected than any other products of combustion. I've seen the aftermath of what it can do to people.
Derby, one earlier thread actually endorses smoking a few cigs a day, with varying results, I would try that route first. (as you have clearly started!)