@candacendiaye: A few different issues here...
First just a quick note. We've heard of some known conflicts with the Headway theme. One person says they resolved those by disabling the theme's option for "gzip compression." Can you try that and see if it resolves the thumbnail and lightbox issues?
CAPTIONS: I'm not sure what you were going for here. In the past, the only ways to display captions were using caption templates for thumbnail galleries or the nav bar for basic slideshows. Were you doing either of these before, and if so, did they stop working? To use a caption template, you need to add a thumnbail gallery, choose the caption template, and set a number of columns to keep the alignment good. Let us know if you are looking for something else.
THUMBNAIL LAYOUT: Sounds like you are seeing a single column of thumbnails? Can you please post a link so we can see?
On this, first try disabling gzip compression on your theme as noted above. Otherwise, the only times we've seen that in the last few months, it's been caused by a plugin or theme conflict, generally a caching plugin. If you have a caching plugin installed, try clearing cache, or deactivating and reactivating your plugin, or go to Gallery > Other Options > Misc and click click "Clear Image Cache". If those don't work, you might consider momentarily deactivating all other plugins except NextGEN just long enough to see if it goes away. That will tell us if there's some kind of conflict.
LIGHTBOX: This also sounds like it may be a conflict. Again, first try gzip compression for your Headway theme. Next, can you please try changing your lightbox effect at Gallery > Other Options > Lightbox Effects and confirm if any of the lightbox effects are working?
If that doesn't work, I'd again recommend momentarily deactivating other plugins just long enough to see if that resolves the issue.
Try those steps and let us know if any of these issue are resolved.