vurt

You need to recreate a layout a bit, then everything will be fine without using code
When you add text, please add a Line Block here

Then save page > Then edit page > then remove Line Block
 

That block of code will affect all blocks. You should be able to achieve what you need with some code that targets the images more specifically. The exact code will depend on the page, the blocks you've used and the way they are laid out.

Yes, it was the guide to using index pages. 
https://laurentaylar.com/blog/squarespace-index-pages 
It seems to me that what you want to do is easier with image blocks and gallery blocks on a page that is not a gallery section but can be a page in the index. If you can post your website address so we can take a look that might help us to help you easier. 

I think you can adjust the caption fonts in site styles.  Spaces between image blocks and gallery blocks can be adjusted with a combo of padding controls in site styles and using spacers on the page as well. Spacer blocks can be a bit tricky when positioning them, Watch the vertical blue line and make sure it doesn't "grow" up beyond the block you are working with, or your whole page will shift. 

Hi,
You should contact Squarespace Customer Care to ask this for a reliable answer.

The link is going to a blog post not the blog listing page itself The actual blog page is here.
https://www.lammay.co/happy-brides/  notice that you have a title of your comments page, and there is no comments section at the bottom. 
The post where folks leave comments is a post in the blog. Why you can't see your blog page with the a in config, I can't explain it. If you don't see it you will not be able to create a new post.  When on the blog post page hit your  escape key and then log in if needed. It should take you to the settings for that page. 

Reviews is not the blog page, it is a link to the page. The actual blog page has a small a on the left side of the page in pages under configuration. Click the a panel will open on the left with all your blog posts listed there. Then click the thumbnail of the one you want to change the title to. The edit and settings panel opens up and the title is on the frist line of that panel. You will notice a small arrow up on the right hand corner of that panel. When you click it it opens the content of the post for full screen editing, the settings tabs go away until you click that arrow again. 

Using 7.1 go to pages, click on the blog page, click the thumbnail for the post you want to edit from the list. Click edit up in the top left of the panel that opens, then click the actual title of the blog. A vertical line appears and at that point you can edit the title or delete it using the backspace key. 
If you are wanting to change the blog page name, go to pages then click the gear icon next to the blog page, the settings come up and you can change the name of the page, and the navigation name there. 

I don't know if this is right or wrong, but I managed to adjust the height of the header with this code:
header#header { max-height: 110px; }