You only have 42 listed there and there are 59 total??? Yes you only need 42 to complete the 100% but there is no specific 42 you need to do. So yes the bounty missions and the arms traffic missions count. Plus I know this first hand because once I completed the game I started to really work on my 100%. With that being said I had totally missed the bounty missions so I went back and did them all and yep, I got 4 added to my total of 42 for the 100%. Plus the arms traffic do count but you are partly right. The first few for until you pop the arms race achievement will count but not the countless afterwards.
Now I know what IGN says and I do indeed follow IGN and really like the info there but I need to disagree this time. Like I said, they did count for me for sure. That I am positive about. But like so many other things with this game, It may be just another problem for them to fix.
Actually, if you go to http://socialclub.ro...areer/checklist, you can see that, in fact, the bounty missions are not required for 100%. The only hobbies and pastimes that are have a small vertical green stripe next to them.