What's the max current on pin 23 and 35 MC41 FS

These are the -VREF pins. 

As these are intended to be used for sensor ground, the current the pins normally see is what the +VREF supplies. But the pins are designed to cope with higher currents in order to withstand short circuits. 

Continuous currents up to 8 A should be safe for avoiding damage, but could be problematic for sensor readings if you have this amount of current and also ground sensors via the -VREF.