I would like to download all images and attachments from this section only:
How can I achieve that?
One other thing: sometimes there are just thumbnails of images that point to an EXTERNAL domain included in posts, such as Imageshack, Photobucket, etc. I mean those thumbnails are linked to an external page that has in it the full image that I need to download. I find that full size image hard to get. What to do?
"Download only posts from the forum topic"
Use the URL you specified here. If you need to get external images. If you want to get external links, I could suggest to change the URL Filters - Server section - check the "Load up to 1 links on external servers" box. Click the OK button and make the download.