I have similar hardware (late 2011 MacBook Pro, with 16GB of ram and an SSD). By installing winetricks and using the Useglsl=disabled tweak mentioned by Kipsauce in the Linux tutorial thread, I was able to get the game playable. Some areas slow down, so it's not perfect, but it's worth trying.
Limiters can be unsealed at 20k kills, so it wouldn't even require the effort of even 1 kill to unseal. The fact that you refuse to unseal them even though it wouldn't take any effort to do so suggests the limiters you are planning to trade don't actually have 20k kills. aka it's a scam.
No offense meant, but from a buyers perspective this looks like a scam. The buyer has no way of telling the number of kills until after the trade it complete, so they have no way of knowing if the limiter in the trade window is the same one in your screenshot or a limiter with 0 kills until...