You might as well do an accurate simulation and do 4 x 500 on 30 seconds rest and do them around 7:00ish. Hold consistent pace the whole set with no drop off in speed. I think people can get a false sense of their pace based on the 100s or if you do the 100s you should descend as you do the set.
Pretty close to what I was going to say. But I'd go 4 x 500 at 7 min per steady to hard, on 8 min. take off. When you can eventually do that, graduate to 2 x 1000 on 15 min take off with target of 14 min. Then you're ready.
In the race, you'll have to use some extra skill of navigating super straight on some slightly faster feet, with a wetsuit--you'll nail it provided the course is measured accurately.