No. Samsung J7 Max is not water proof.
Yes, Galaxy J7 Max does have LED Flash for the front camera.
Yes, Samsung Galaxy J7 Max does have FM radio.
Yes, Samsung Galaxy J7 comes with non-removable battery.
Yes, you can put 2 4G SIMs and a Memory card also at the same time in Samsung Galaxy J7 Max. Galaxy J7 Max does have 2 dedicated sim card slots and a dedicated slot for memory card.
Samsung Galaxy J7 Max is worth considering if updated software and a great camera are your priorities.