#3 Is it possible to replace one of the omni directional antenna with an RP-SMA cable from one of those 24dbi antenna and use this AP as a repeater?
Yes! You can detach one antenna and easily connect an RP-SMA external antenna. This is how mine is setup and the reason I bought this WAP. I'm using a TP-Link 9dBi directional antenna which doesn't require any additional power and it works great. I'm getting full bars at 75' away.