Put [Peak Flow Calculator] into Google, fill in the blanks and you can get an estimate of what your PF should be. This is based on statistical norms so being a little over or under your estimate is not cause for much concern. Being way under the mark is a problem. The tool is far more useful for asthmatic and checking to see if the are having an attack/deterioration, how bad it may be, and if they respond to their medication.
PF tests LARGE/UPPER airways. COPD affects smaller/more distal airways down to the alveolar level. As stated previously, you really need a full spirometry to get that info.
Pretty much everyone is mad at themselves for ever starting smoking. If you are under 20 and smoke, you think you are cool. Over 20 and they know they are addicted even though they seldom admit it. Most people start smoking in their early teens when they have absolutely no concept of being older....ever. By they time they get a clue it's too late.
Interesting anecdote - I worked for a homecare company for about 12 years. Their main product was O2 delivery, and the vast majority of that went to (almost always) ex-smokers that had really bad COPD. I saw a lot of these people. Only ONE guy freely admitted, "I did it to myself, it's my own damn fault". Most hid behind some excuse like "my Dr. never told me to quit", or "no one ever told me they were a health hazard", both of which are usually complete BS.
Warning labels came out in 1966, and they were commonly referred to as cancer sticks long before that. The entire industry is full of deceptive, amoral misanthropes. Smoking as a costly health problem far exceeds the costs of ALL other drug related problems combined, legal or illegal. That is completely ignoring the social and personal costs.