I recently bought a modern li-ion 21700 light, and have a few questions.

I'm coming from Nimh... so I have some quick catching up to do.

I understand DIY'ing a light.. you can match driver type to Amps.. just not how many Amps go with what drivers in off the shelf lights: Zebra, Fenix, Acebeam, Nitecore, etc.

My light is a Fenix Tk22UE with their 8A cell. I know the light doesn't use all 8 Amps.. based off of the SST-40 spec sheet, it's closer to 4 maybe 5 max.
I know some might say 4A from 8A is fine but, that's around 50% capability of the cell, and it's too close for my liking.

After dropping my light twice while using it, I checked the cell and saw it was dinged a little bit on both ends.
It instantly made me think of some people here, and the risk of the protection circuit "possibly" being damaged when it needs to be charged.. I'm sure it's fine but... that little thought in the back of my mind.

First question is:

1. The light has a digitally regulated circuit, and a low voltage warning. So, if I made sure to pay attention the the L.V.W, or just the brightness step down.. is it okay to use unprotected cells with the addition of a D.M.M?

2. Fenix just came out with a 10A cell, and I know I can use theirs but.. could I use anyone's 10A cell without harm? 10A is 10A, right?
Or do I need to worry about the I.R. of cells, and risk blowing the driver from current availability?

3. Is it safe to use any amp rated cell that's above what the emitter needs? I.E. 25 to 40 amps? I know there wont be an much of an improvement --if any.
It'll just be at the lower end of it's performance curve.

I have a charger in mind of getting.. a Vapcell S4 Plus.

Okay.. crash course over.