2 & 3. HART and Caldwell were asked this in a hearing and their response was "we don't know" "we don't have the numbers" "we'll get back to you"

And I think rail is the worst idea and was bungled because of incompetence and poor planning but 
4. Oahu subsidizes the neighbor islands' existence so I don't see what the problem is. Especially since Sen. Inouye tried to add a provision in the Senate version of the bill to funnel money from Oahu only GET into DOT's highway fund that is predominantly used by neighbor islands.