Got a question. What defensive scenario are you going to be in that will require you switch magazines to FMJ to shoot through a barrier? And if shooting through a barrier, how are you going to know what your shooting at?
I might see some situation when your at your home, maybe, but can't really think of any when out in public carrying.
As far as FMJ, if it works in your gun, why can't your use it for defensive purposes? Any of it should be fine. Your Speer should be fine if you choose to use it in one mag.