1. How can I get them to fit the screen properly? See the screenshot. Also, you can see a button with that problem at the bottom of the post here
The text is too long inside a button and buttons with 2 lines are not a standard behaviour. To fixed this you will need to manually apply a hack on it.

2. How can I make the button color match the rest of my site? I am using the Simplistic Easyblog theme. I actually want to use buttons that are the same as on my home page. I tried using the same classes for my buttons on Easyblog, but Easyblog does not recognize the class I want called "button button-red" Do I need to modify the CSS in the Easyblog theme to make them match? If so, how?

3. There needs to be a space to separate the bookmark icon on the blog post page. See the screenshot below. How can I add this space to make it look better?

1. Where do I put the CSS you provided? In what file?

2. I'm sorry, I was referring to the solid buttons on the home page. See the screenshot below. I like the current button shape, but the color I want is darker red. It is dark red that becomes a little lighter when you hover over the button. The colors are db0000 and #c10404. It looks like the bootstrap button colors cannot be changed, so I was using a custom button class called button-red. Unfortunately, it displays properly on my other joomla pages, but not on Easyblog.

I changed the class to button button-red in the same post mentioned above, but the red background of the button does not show at all. If you see the same post again, you will see that the text and link are at the bottom of the screen (in white), but there is no visible button. You can see this in a screenshot here too