100khz = 10uS
Diode Tff = 0.1uS
So you will be in rr mode 1% of the time. I think the diode will be hot. (I think it will be OK but watch the temperature) That diode is fast and I don't think you will find faster. I am surprised you found any diodes like this. I used to use millions and then every one stopped making them.
I have designed may 27kv 120khz power supplies. I did not use "square wave" but I did use resonant mode. (half sign wave) In my case the transistor is on for 5 to 7uS and off for 2 to 3uS. The off time is half sign wave. There are no sharp edges. So I could use this type of diode with no problem.