RWD could bring in BHP, RIO etc. to use their rail. However, it...

RWD could bring in BHP, RIO etc. to use their rail. However, it would be the intangible benefits that would provide the biggest benefit. RWD would get access to their global networks which include business and government leaders. 

Offer them half and then focus on acquisitions of other global potash projects over the next few years using their connections (while bringing LD online)

Chinese income is growing so agricultural products will be in demand, therefore, so will MOP and SOP. 

The reduction in tariffs is just a political game between China and Trump. They are reducing tariffs on products they deem to give something while still holding major cards. Therefore, the tariffs could be back up again soon