Help me with Internal Server Errors on my Wordpress blog - fix and help redirections

I've got a website (http://www.footyblog.net) which is running Wordpress.
I'm using EUKHosting (cPanel Linux Platinum) with a Dedicated IP.

I've been having a lot of issues with my site for a while. For example I visit the site and theres a page cannot be displayed error. I refresh and it will load, sometimes I have to refresh several times.

I had quite a few plugins installed, someone said it could be due to a cache plugin. I disabled all plugins but was still having similar page cannot be displayed issues.

I've used the Screaming Frog SEO Spider and when I run this on my site it brings up a lot of Internal Server Errors (I've got a copy of the crawl file, don't know if this is any use, I can email it over if so).

Previously I had someone help me to set up the site and they put in quite a few redirects. I don't know if this has been done correctly, as the SEO goalposts often change, and now maybe they're seen as bad SEO tactics (redirecting pages to my homepage and so on).

So I want someone to come in and fix my server errors (or recommend me a new server if they think this is the issue) and to take a look at my site setup and check that the structure is okay SEO-wise. If there are any dodgy redirects etc, to recommend what to do to fix it.
My website used to rank really well in the search engines but now it hardly does at all, and I think I'm likely to be getting penalized for all the server errors. I can give access to the necessary accounts (Webmasters, Analytics, Hosting cPanel, Wordpress...)

Any questions let me know, thanks!