You could use a device that has a PCA. Put the clock source to F(osc)/4 (mode 1) and setup a PCA capture on + and - edge. On the '+' interrupt, you can determine the frequency, on the '-' the duty-cycle (or the other way round, whatever you choose).

However, for a 100 kHz input signal you would still need a top-speed device to get at least some decent results and you won't be able to detect absolute max. and min. duty-cycles.