I think you'll find the THC min speed is the point where anti dive kicks in, I.e. The minimum % of set cut speed that it starts anti dive, I have mine at 90% so I think that if speed drops to below 90% of my set feedrate it will not dive the torch.
Small holes I am still learning but, if you set a lower feedrate in gcode, it will not allow anti dive to work because the feedrate is now lower. What I am doing is to split my small holes out in cam and apply a manual THC off command before it cuts and THC on after, before going back to full cut speed, this seems to work but...
I have also just found that by tuning my speed and acceleration figures on the table, I don't need to slow down manually apart from small holes in thicker material which I do as described above, I can do a 10mm hole in 5mm plate at normal feed and let antidive deal with it.
Yes, I think if you change cut parameters a lot, I think you may need to up the THC rate a bit, possibly.