Your remote has setup codes 30842 and 30135, not 31531. So EFC 58052 won't do anything except what happens when you press those digits individually (AM radio apparently).

As 3FG said, no toggle exists for the SR700 according to Onkyo's documents. The solution you posted in post 3 is your best option:
"30135 works fine but is only power on. 30842 works only to power off but by pressing setup-power. "

If you don't mind spending $8 on a programming cable, you can load some code that will allow you to make your own toggle using a toadtog bit. Otherwise, stick with the primary and shifted button method.