Small correction, it went from -41.3 dBm/MHz to -31.3 dBm/MHz. I would recommend to also look at this forum post regarding the regulation: Question on Updated UWB Regulation in Europe (-41.3 dBm to -31.3 dBm)
All other variables being constant, a 10dB increase in TX power, would cause a 3.16x increase in the distance. This is 20log10(x)=10 → x = 10^(10/20) = 3.16
We have had customers use antennas from a variety of manufacturers including Abracon, Kyocera, and Taoglas. Others have designed and printed their own antennas on their PCB.