Correct Error 500 issue on wordpress site

My site is a dating site landing page and blog page that uses wordpress and integrates with a white label site for the database and profiles. Over 2,500 crawl error 500's are showing on Google Webmaster tools. I need someone to correct this so Error 500's are removed and shown as zero. These are urls that the Google bot shouldn't even be looking for but somehow it is associating them with my site and recording it as errors. Clearly these errors are responsible for a Google algorithm penalty. My website was ranked on page 1 for Google for two popular keywords and it is been put down to page 75 after this problem emerged I used a website developer to create a new blog and the errors have shown up since then. He can see any reason for the errors. He removed the Word Press plug-ins and waited for Google to crawl again but the 2,500 plus errors remained so this indicates this is not a plug-in issue. I have contacted the host (Host Gator) and they do not see any error 500's in their log. It's not a straightforward thing so therefore want someone familiar with resolving error 500 issues to bid. I confirm again that payment will only be made after successful resolution i.e. 500 errors no longer showing in the diagnostic section of Google Webmaster tools. The resolution must include correcting rather than removing the blog page. If you want my website domain and any examples of the error 500's showing up before you bid then please PM me. Also the white label dating company I use to link with to get the profiles and dating database is this one [login to view URL] but please note this is NOT my site - it is only the site my landing page integrates with.