I immediately raise all in for another 14 on top of his (3/4ths of his stack) and am all in. He immediately calls, and shows: Js 6h. 2nd pair, no draw.

Board is [Ks Qh 2d 4d Kc]. I immediately go all in for 13 (about 1/3 of his stack. He think...thinks...thinks.....calls down with 6d6h.
At this level, outplaying your opponents is a tricky dangerous game. You're better off making a hand, pushing hard, and letting them call you with worse hands. You're trying to row upstream, and it's not gonna work. Stop bluffing bad players unless A: You know almost for certain they will fold, and B: You plan to show and tilt them later. I used to bluff into these players only when I had tremendous fold equity, and even then I would still get called and beat sometimes. Think about how low your opponents calling requirements are, and ask yourself how much value exists in the technique of lowering it more.

If you never bluff at this level, you'll still make good money. Keep that in mind. I'll go down there and bluff my azz off in the right spots taking stacks in other spots, but it's not that simple a thing. I maximize value when I really have no need to, because I have fun doing it, and don't care if I lose 3 buy ins messing around. My variance goes through the roof, but usually I can leave with a huge stack for my efforts. You're a long way from that still it seems.