Running out of memory when exporting from Premiere or Encoder

I think I may lose my mind if I can't sort this out. I've been trying for 8 hours to render a 45 sec video. I have 15 still images with a Transform Effect on each. Basically a Ken Burns slide show with a "Dip to White" transition between each. Admittedly the images are large-ish (3000 - 5000px, JPGs), but the thing that is totally driving me crazy is that yesterday I queued up 6 variations of a very similar sequence in the same project, on the same hard drive, with the same images, the same effects, and the same sequence and export settings, and I had no troubles at all, while I simultaneously used Chrome and Word. I haven't updated anything or changed my system configuration in any way since yesterday. Today all of the sequences are crashing at approximately 12%.

I have trawled the forums and tried EVERYTHING.

Every time I export this sequence, either through Premiere or Media Encoder, it goes very slowly, the available RAM drops to 1GB, and then the exporter stops at about 12%. It will either give me a dialog which says " Your system has run out of application memory", or it will stop responding and I have to Force Quit, or it will just stop exporting and sit quietly doing nothing.

These are the things I've tried:

• Quitting all other open programs
• Project managing the sequence to create a new project that only has the files used in this particular sequence, and re-exporting from the new project
• Exporting from and to two different external hard drives and my system drive
• Clearing the Media Cache on Premiere and Media Encoder
• Changing the scratch disks
• Making an extra 100GB available on my system drive
• Using Memory Clean after sending the sequence to Media Encoder
• Updating my CUDA Drivers
• Changing the Renderer from CUDA, to OpenGL, to Software only, both in Premiere and Media Encoder
• Turning off "Automatic Graphics Switching" in the "Energy Saver" System Preferences Pane
• Disconnecting from the internet
• Removing the image that was there at 12%
• Deleting my settings folder and turning off Settings Sync so that Premiere starts with default settings
• Restarting my computer at least 6 times
• Crying softly and disbelievingly

UPDATE I also tried upgrading to MacOS Sierra 10.12.6. No luck.

Does anyone have any further suggestions?