Don't believe what the forum says for the maximum size. You should be able to upload a screenshot without having to resize it. The forum will reize it down, itself, for display in the message but clicking should bring back the full-size.
The dropbox link you've provided is for your own user not the general public. Please provide a public download link for each image, indicating which is the before-PS and which is the after-PS version. There should be something in the dropbox interface that specifically has Public in the phrase. Maybe you have to right-click.