...fixed links.
Ed...just follow these steps:
Go to your Gallery.
View the Medium-sized desired image (not the big version).
Directly below the picture is a section entitled Photo Details; there, further down, is Additional Info, with four cutout boxes with 'code' in them
Just click-to-highlight the stuff in the third cutout box labeled "Medium Image:"
..then point to the highlight and COPY with a right mouse click.
Go to your post and, at the desired place, PASTE the link.

Oh...wait...you have a Mac, right. Sorry...no right-clicks for you.
Just copy and paste the Medium Image: link into your post.