Pre-flop, this would normally be a 3-bet at NL2, although there are some reasons why you might want to flat this hand in this position (e.g. if you 3-bet SCs and don't want your 3-bet range to get too large or if UTG is a nit).
Frozenelf's maths is unfortunately not completely accurate. Given a probability p that an event will occur, the odds of it occurring are (1/p - 1):1. So for example if an event is equally likely to occur as not, the probability is 50% and the odds are 1:1 (where Frozenelf's formula would incorrectly given you 2:1). However, it may be easier just to look up the odds on a table like this one.
The rule of 2 and 4 is good enough for most practical poker purposes. Your actual chance OTF of improving to at least a pair by the river is 24.14% and your odds are 3.1:1, so your numbers are close enough. OTT you've applied the rule of 2 and 4 correctly, but the odds calculation is wrong. It looks as if you've added 1 when you should have subtracted, so you've got 9:1 when you should have 7:1. The true probability is 13.04% and the true odds 6.7:1.
Your calculation of the pot odds OTF is incorrect, which is strange, because that ought to be the easy part. OTF there are 38c in the pot and you're asked to bet 12c. Your pot odds are therefore 3.2:1 (a half-pot raise always gives pot odds of 3:1). OTT there are 68c in the pot and you're asked to bet 18c, so your pot odds are 3.8:1 (it looks like you've just made a rounding error here).
Unfortunately, you've calculated the wrong thing. On the flop, you're not interested in your odds of improving by the river (unless you're going all in). What you care about is your odds of improving on the next card. You can see the reason here, because when you don't improve and the villain bets again you're forced to fold so you never see the river. You have odds of 6.8:1 of improving on the turn and you have pot odds of 3.2:1. So you need to expect another 3.6 times your bet (in this case another 43c), which will be roughly equivalent to getting villain to call a pot-sized bet when you hit. Your problem is that if an A hits the turn and you bet the pot, it's going to pretty obvious what's happened. Plus the villain is betting in a 4-way pot, so he could well have a set, in which case you get killed if you hit an A or K. So looking at it that way, this should be a fold.
However, it's not as simple as that (of course), because we also have to consider the possibility that the villain is bluffing. I think quite a few players at NL2 are betting in villain's spot just because he acts last and sees that no-one else appears to like the flop, so he can steal the pot. If he has overcards, you will have the best hand.