so I've found the concept of MDF to be very useful recently, and I am trying to implement it in to my game as best as I can. but there's one thing I don't get about it and would appreciate if anybody could answer this.
so on the flop villain pots it and is risking $10 to win $10 thus needs to work 50% to break even and greater than 50% for him to have a +EV bet. I get that bit.
what I am struggling to figure out is when we bet river and get raised, because he is still risking the same amount to win the pot but we have better odds because we have already put out a bet and gotten raised.

example: we bet $50 in to $100 on the river and villain raises to $150- so he is risking $150 to win $150 so his bet needs to work >50% to be +EV. but our MDF can't be 50% any longer can it?? as we have just invested $50 in to the pot.
where as before we needed 33% equity to call now we need just 25%. is our MDF still just 50%??

and again, a bit more of an extreme example, we are on the river and bet $100 in to $1 and opponent jams for $101. so he has risked $101 to win $101 thus his bet needs to work >50% to be +EV. but we only have $1 behind so we need 0.5% equity to call this jam. what is our MDF for calling this river just getting over 200:1??

TY.