People date in the workplace all the time, so I don't think your rules about "professional situations" are generally accepted.
I also reject the notion of "position of power" just because he is a VC. Nobody is forced to take his money. You could just as well say the applying women are in a position of power because the VC desperately needs somebody to invest in. I guess a startup should avoid seeking investments where the investor is "in a position of power", anyway.
I am also not justifying his behavior, obviously he made mistakes. But I reject the immediate interpretation of "man abusing his power to pressure women into sex".
The "boundaries" talk is also not really helpful - at some point, somebody has to make a move. If their estimate of the situation is correct, they are not "crossing boundaries". Otherwise they are crossing boundaries and need to withdraw.
Grabbing a knee under the table is of course not a good first move, but we might be missing context.