it’s still not entirely clear what you have.
there are a few possible options i can see:
1.
film was telecined at 29.97, so that every frame of film corresponds to a frame of video.
this is good as you can do more with the film in post,
but you have to do a decent speed change on the footage
i dont think you have this.
2.
film was telecined at 18fps
obviously 18fps doesn’t go too evenly into 30 fps
so there is most likely blending of the S8 frames on every frame of video.
this can make it a little bit harder to edit as there can be 2 images on a one frame, at the original cut points, but it’s not a big deal
really the question is does it look good to you?
if the answer to that is yes,
then the answer to your original question is easy:
edit in a sequence that matches the file you have.
and there should be no need to alter speed at all.
nick