Subdomain to Subdirectory half worked?

I’ve moved my site following the wordpress moving your site guide and a few others, and it mostly worked well.

The old URL: blog.asseenontvhot10.com
Now redirects to the new URL: https://www.asseenontvhot10.com/blog

But the post links from other sites aren’t updating, for example: https://blog.asseenontvhot10.com/eggtastic-poached-egg-recipe/
Should redirect to: https://www.asseenontvhot10.com/blog/eggtastic-poached-egg-recipe/
Instead I get a 500 error.

I also think that some of my CSS got broken, which worries me a little because I don’t know what else may have gotten broken, I used to have a background image and had changed the colors of a lot of the elements. I thought that maybe my custom childtheme css got messed up, but it looks like some of the code I wrote is still there. If I need to reskin my child theme I’m fine with that, but I really need help with the redirects.

Here is my htaccess code:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /blog/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /blog/index.php [L]
</IfModule>

# END WordPress
RewriteCond %{HTTP_HOST} ^blog\.asseenontvhot10\.com$ [OR]
RewriteCond %{HTTP_HOST} ^www\.blog\.asseenontvhot10\.com$
RewriteRule ^/?$ "http\:\/\/www\.asseenontvhot10\.com\/blog" [R=301,L]