Start low and if you want more you can add more to the fermenter.
I don't know. adding fresh ginger to the fermenter might well result in biological activity that you did not intend. Lots of critters living on/in ginger.
I buy on, but in? I added a pound of peeled ginger to a fermenter once and didn't see new biological activity. Took a year for the ginger to mellow out though.
well there you go. I guess if your careful peeling and don't contaminate the peeled ginger too much it might be fine.