I know you're talking about steps 3 + 4, but this might help in the meantime for steps 2 + 3:

1 - Images
Save all images to the same folder

2 - In PPT
Insert > Photo Album > New Photo Album
Insert picture from: File/Disk >> select all images in the folder
Album layout:
- Picture layout: 2 pictures
- Frame shape: Center Shadow Rectangle - or Soft Edge Rectangle (Glow is not available)