I don't know about the charger that came with your light. I would just watch it very closely for the first few charging cycles and make sure that it cuts off when your cells reach the correct voltage. It should work properly with any 18650 cells, as long as the protection circuit of the better cells doesn't make them too long to physically fit.
There are many topics on BLF about 18650 batteries and chargers, i am not the expert.
I use the blue Trustfire protected 2500mAh lithium-ion 18650 batteries from DX, these do not have the highest capacity, but even the oldest (2,5 years old) are still working fine. But there are much better 18650 batteries.
Don't know but most posters here have chargers and batterys already. The 1600 lumns is false likely 700 lumns or less! Probably much less! And I think the 2400 batterys listed have problems. I've been burned more than once on E-bay and now usually order from China dealers checked out by the members here. I trust some of the statements made by BLF members far more than China ads or E-bay sellers.