Re: Why was 21 million coins chose as the total number of bitcoins?
Total number of bitcoins to ever exist is 20999999.97690000, a little less than 21 million. 
No, as discussed on this thread:https://bitcointalk.org/index.php?topic=1029082
at least "150 + a bit" of those coins never existed in the first place (3 unspendable coinbases + miners refusing the full reward + fees).