I might be able to address duration. There is a website called ORBIS, which calculates travel distances and itineraries during the Roman Empire.

Although clearly the First Crusade is not during what is what we think of as the the Roman Period (though the Eastern Empire was still struggling along in Anatolia and Greece, having recently suffered a devastating defeat at Manzikert), we can perhaps use it as a guide. It told me that:

The Fastest journey from Ierusalem to Roma in July takes 28.4 days, covering 3192 kilometers.

(the fall of Jerusalem was on 15 July). That's assuming high priority, fast sea transport, and road travel at 30 km/day. Assuming slow sea transport extends this to 39.5 days.

I suspect that long distance travel was more organized during the height of the Roman Empire than it was in 1099, however, this would have been a very high priority message, so I suspect that the ~month travel time would be close.

ORBIS is great fun to play with; I recommend it.