I grew up with the Dos version of Lemmings, and so I knew about horizontal movement with diggers and builders. As you can see, that's the only way through the flame/ice blower area, especially if you want to save 100%. And yes, you're right about just building a spiral staircase for the exit area. As I mentioned, mine is just one of many, many ways to do the level. Now that you have your own replay for Hellish 20, you can now add it to your zip file in the OP and reattach.
Luckily, Sublems is already available for Superlemmini. As for the NL version, a lot of the Superlemmini levels got replaced with new ones, either because they were unpopular or Arty wasn't able to convert the Superlemmini level to NL and hence replaced the level. So, be aware that some of the Superlemmini levels aren't present in the NL pack.