"How far it will go" is best interpreted as a question about free space propigation loss. As a practical matter, a free space propigation calc would show a FSP loss of about -130 dB at 100 miles, which given a transmitted signal of 50 dBm would result in a received signal in the range of -80 dBm, which should be receivable on virtually any receiver.
But that doesn't mean you can service an area of 100 miles radius in real life. Rather, in real life you're asking what the usable service range for a transmitted signal of 50 dBm from an antenna with an HAAT of 88.7 m (291 ft) over reasonably flat terrain. For a reliable answer for any particular location, you need to get your hands on a propigation survey software package (very expensive) and someone who knows how to run it (ditto), but I'd guess that as a general matter your signal should be reliably heard by a well-installed mobile or outdoors portable within about 20 miles.
That, however, is for the output. The workable range for input signals is an entirely different animal, and you have to know a lot more about local terrain, system parameters, and other things.