I'm not even certain Sarver owns half the team. There are 15 partners in Suns Legacy Group, one of which is Steve Kerr. If Sarver were hurting that much, I'm certain Jenny Craig, Steven Hilton, or any number of others could bail him out and help him divest his interest in the team.
Heard he controlled little over 30% when the team was purchased not sure if it's accurate.
As far as GM salaries. The league average is 1.5mil per but interestingly some guys take less than market value to run the team. Sam Presti was the lowest paid GM when he signed with the Sonics shunning more lucrative deals because he wanted total control. Pat Riley is currently the lowest paid, but again has complete control of the team.