To your first question: yes, the reset all stations command (http://os-ip/cv?pw=xxx&rsn=1) will do it.
To your second question, yes, you can change the controller enable bit (http://os-ip/cv?pw=xxx&en=0) to prevent any station from running. Note that each program also has an ‘enable’ bit, so if you want to allow some programs to keep running but disable other programs you can also set each individual program’s enable bit.