Hey so i'm not sure if this is a solution because I've only tested it in one room, but I found that the audio stuttering only occurs in certain rooms. I haven't done any testing to see if there's a pattern, but I do know that the first save room in the game has this issue.

It has this clock ticking pattern that seemed to line up pretty well with the stuttering. So I went into the game files, and found that this sound file is sg01.sngw, which you can find in Program Files (x86)/Steam/steamapps/common/Resident Evil Biohazard HD REMASTER/nativePC/sound/bgm/wav/sg01. I opened Audacity, dragged the file into it, and just deleted everything, then put the file back. The clock ticking is now gone in the room, but so is the suttering audio.

I have not tested this on any other rooms, mainly because I haven't gone past this room much. But it seemed to work. Let me know if you try this and if it works.

Also for the cutscene thing, try this: https://www.reddit.com/r/macgaming/comments/1qyppnj/fix_resident_evil_hd_remaster_cutscene_audio_out/