Well you dont have to convert it to iso and perform a regular install. The .wim is catered for your system so you just need to sort of restore it.
Boot up in Hiren's WindowsPE or any other, and use something like GImageX to apply the image.
Monitor the temperatures and see whether the CPU and GPU are throttling (they probably are).
If it is due to temperature then re-paste it with any good thermal paste. Personal experience.