I have added Fifty50 tournaments to the registered version of ICM Explorer. SNG Wizard has an update this week which computes Fifty50 equities, too.

Basically, you can imagine that Fifty50s are half DoN and half winner-takes-all. I'll go into more detail in my Fifty50 theory video.

I don't know the right way to handle knockout SNGs. In one simple model of how players are knocked out, your chance to knock out each player turns out to be your proportion of the total chips, so as long as you aren't knocking someone out on this hand, you can approximate the equities by a weighted average with a winner-takes-all tournament. That is based on

this model, not diffusion, and I think you may get different results with a diffusion model which might be more accurate.