Just a couple general comments. I may be able to offer my experiences but in the end, you are the only person to convince yourself to play the way you do. Go with what you feel is right. Just make sure to review your play and learn from any mistakes you make. Heck, I may be offering you bad advice so make sure you can organize and comprehend it in your mind before taking any of my advice. I'm not a coach or anything but maybe gallopingael would have some input on some of the stuff we discussed.
Now onto why fish are +EV to play against:
$5.20 Buy-in (300/600 blinds, 60 ante) No Limit Hold'em Tourney, 6 Players
by Stoxpoker (http://www.stoxpoker.com/) - Hand Details (http://www.stoxpoker.com/pokertools/hand/75326/)
CO: 2,710 (4.5 bb)
BTN: 3,105 (5.2 bb)
SB: 2,920 (4.9 bb)
BB: 2,205 (3.7 bb)
UTG: 2,050 (3.4 bb)
Hero (MP): 2,010 (3.4 bb)
: Hero is MP with 3♣
2 folds, CO calls 600, BTN calls 600, SB folds, BB checks
: (2,460) 9♦
K♦ (3 players)
BB checks, CO bets 600
, BTN calls 600, BB folds
: (3,660) K♥ (2 players)
CO checks, BTN bets 1,800
, CO calls 1,450 and is all-in
: (6,560) 8♦ (2 players, 1 is all-in)
[spoil] 6,560 pot
Final Board: 9♦
CO showed K♣
(three of a kind, Kings) and lost (-2,710 net)
BTN showed Q♣
(a straight, Nine to King) and won 6,560 (3,850 net)
This hand is a little bit of a cooler but the plays the fish make are lol so it illustrates my point.
The BB, UTG and Hero are about to be crippled by the blinds. However, CO and BTN decide to spew off some chips by limping (awesomeness #1). Next, CO flops top pair Q kicker and min bets while BTN flops the nuts but decides to slow play on a drawy two flush board (awesomeness #2). Turn gives CO trips who decides to slowplay his "monster" and check/snapcalls the BTN's bet. Holecards are flipped face up, UTG and Hero smile, and the game is over.
Now obviously the shortstacks benefit from this particular flop (though I guarantee you BTN can't get away from a Q high board) but limping here by both the CO and BTN are terrible and are the kind of -EV plays that make fish, highly +EV to play against.