Yes but you can control *where* they "kill" each other.
No, you can not.... Weather and all other kinds of things make this point change day by day and even miltiple times a day.
It is a big misunderstanding that this can be done. Really impossible. Ask engineers...
Oh, I don't know. There's a MaxxCasting installation in Seattle which has impressed the local engineers, many of whom have had some exposure to SFN and its foibles.
The station involved is not one of my clients, but one of their MaxxCasting installations (there are 5) is on a client tower of mine. Where I've listened, it has very little of the normal interference and has proven to be stable, so far as I've been told.
In addition to the typical synchronizing methods this system uses a series of highly targeted directional antennas, each with very restricted rear contours. Basically, the goal is to keep the signal going in the same direction from the originating tower, thereby reducing the interference area that's common when a booster's signal crashes into that from the originating tower. In that scenario, and without some substantial terrain shielding, I would agree that any real solution might be difficult to attain.