Homepage posts & Sidebar

I’m currently live previewing this theme and I have a few questions about the homepage:

-it only displays 5 posts and leaves a post-sized gap where a sixth could go before clicking “older posts.” Is there a way to allow it to have a sixth in there?
-Some of the borders are slightly larger than others, how can I keep them the same?

And the sidebar: can I make it so that it doesn’t require clicking the little ‘x’ in the top right? I don’t really think people would know to click that to see it.

Here’s an image of the homepage issues I mentioned.

thanks