Reaper

I dont think it's that long, it would be around 1500 km of driving. There is a looooooooot of ferry though.

When i had Promods i only went to Iceland twice. First time i tried to reach Akureyri and got stuck in the snowy roads. The second time i did a delivery to Reykjavik. 900 km of goddamn curvy roads, i didnt want to do it again xD.

The longest trip i did in ETS2, with Promods, was from Murmansk (Russia) to Timisoara (Romania). Around 3300 km of driving, it took me like 3-4 real time hours to do it, even without the speed limiter.

I spent a fair bit of time in Iceland, I got stuck I think most likely in the same place as you, going up a rather tall peak, and right at the crest I just came to a stop, took a while to get myself unstuck there. I've always got speed limiter enabled, but I don't mind cruising at 55mph/90kmh, it can take a while though, especially with the traffic in some places.

I can't often do really long trips like that in one sitting, I have to save and have a break and a coffee now and again, really enjoying the roads in promods though I must say.