With some creative deal structuring and a little bit of patience and persistence, you can usually get them to see the bright side of what you are doing and you can make a win-win situation out of it all.

If you have proof, I think you'll win.

Foreigners are still a relatively small player in most cities in the US (except NYC and some areas in SF and LA) so the domestic buyer remains critical to prevent a potential correction in the US real estate market.

So I typically decide to work with them to come to a win-win situation for both. 

Carson demanded I send in money WITHOUT providing a PSA (Purchase Sales Agreement), then refused to supply a blank AOM (Assignment of Mortgage) or Allonge for the 2 crappy notes I did end up winning the bid on.

Negotiate with her for a win-win.

Tortious interference would only possibly apply if you got them to cancel/default on their contract, and even if you did, you'd probably win in court, assuming a wholesaler would take it that far, as in Ohio and Fl most of these wholesaler transactions would be violating state licensing laws anyway.  

What incentives (at this price EVERYONE is going to be a cash player) can I offer to sweeten my deal?

The small win that I achieved was being able to successfully trace an owner of a property from a post card that was sent back to me as "return to sender".

A good Realtor will work with you on preparing an offer that will win the sellers over.