Re: wifi dish
A reflector (dish) gives you gain in one direction. The dish is used for satcom, probably 10-12 GHz. You will be using it at 2.4 GHz. In order to realize the same gain as the satellite receiver, you should have a bigger reflector. But anyhow you will gave some gain.
Next thing is that the aligment of the source (the antenna in your case, the horn for satcom) is critical. If it is not in the exact spot it needs to be, you lobe will go in another direction. And that is a pretty big problem because your lobewidth is rather small. This effect is used by so called offset LNBs, which look at different satellites with one reflector. In your case the different antennas will have a beam in different directions. So there goes your MIMO ...
I assume you're trying to make a point to point link? Drop the idea of using two antennas, use a single one and maximize the output power of your WLAN front-end (there are some software tricks to do that) and then you will reach maximum distance. Or buy a bigger dish, it will even help much more.