Looks to be about half a kilometer. The webcam looks to be at about 63.89045405043735, -22.279054215941507 and the main crater is at about 63.88921695342744, -22.269097856211175
The main crater is only a few tens of meters tall.
It's hard if you don't know the precision needed to get to the position you want, easier to just copy/paste and be done with it. How many knows how far 0.001 deg is at a specific location on the globe?
I think you want to divide by 360 instead of multiplying by 360 - when you divide by 360, you should get the linear distance represented by one degree of latitude or longitude.
The camera is located on Fagradalsfjall and the eruption is in Geldingadalir. The exact location of the camera I do not know, but its somewhere in the ~1km range.
It's hard to get a sense of the scale of the scene, anyone happen to know how far away the webcam is from the peak?