[2019] Impale mechanical questions.

It is unclear as every source I find on impale itself specifies something different or not at all..

I am wondering if you leech from the impale damage being inflicted, As well as whether or not Impale Stacks with itself Eg:

Impale lasts 5 hits, If you hypothetically impaled ever hit
First hit 10%
2nd 20%
3rd 30%
4th 40%
5th 50%
6th 50%
7th 50%
Etc

meaning with 100% impale chance you hit 50% extra PURE damage in the above example? (If impale damage is as specified, unmitigated)

And again Is this leechable?

Please get back to me on this one It has been wracking my head in all morning looking at this new tree!

Thanks in advance!