I have tried your settings and it still doesn´t work. I´ve tried G29 in pronterface and it gives me this answer:
SENDING:G29
? (L,R,F,B) out of bounds.

Maybe it´s because my sensor is too far from the nozzle ?
Regarding the Bed size and max Pos: I am using a CoreXY printer and the Max pos is therefore larger than the bed. The printhead has to move about 5-10mm before it can print on the bed and it has about 5-10mm more travel after the bed.