Stuffing Box - Setup and adjustment questions

[GwalarnYacht]

I have just been repacking the stuffing box on my project boat and having some difficulties to get the water drip amount right.

Strangely the amount of water dripping seems to cease when I run the prop, but comes back a lot (to a drip every few seconds) after stopping it. If I tighten it to get the drip amount to about 1 drop per minute, the box seems to get too hot (can't touch it anymore).

Essentially I loosen a bit, too much water drips at standstill. I tighten a bit, stuffing box gets very hot. What am I missing here?

I have packed it with 5 rings GTO Graphite gland, does that seem overkill? Is less better?

At the same time, I have noted the small seacock on top of the stuffing box (see picture), which was not connected to anything so far. If I open the cap, water streams into the boat in quite large amounts. What is this for, how is it setup?