Hi MaryMe - I'm glad to hear from you!! 
I'm sorry to hear about your ex in-law!
Most blockages are not usually stented or bypassed until about 70% blockage, due to surgical risks. However, in some cases they do it sooner depending on the location and the narrowing of the artery itself (like if it's in an area that's curved).
I've gone to the hospital on numerous occasions with chest pain so severe, I just knew I was having a heart attack, however the pain was brought on by angina, but the heart was still receiving enough blood flow to keep it going.
His problems more than likely began long before he quit smoking, they just went unnoticed. Perhaps the stress of quitting smoking put some stress on him/his body. I say this with some understanding, as I was a smoker as well, I've had a heart attack, I suffer with angina, I've had 2 stents placed and a 3rd one attempted, then a triple bypass a year ago.
MaryMe, please let him know that he's more than welcome to come here and join us!!
Bunches of Hugs to you, Teri
http://www.nlm.nih.gov/medlineplus/ency/article/000198.htm