AEM as Cloud | Custom 500 error page implementation

In AEM as Cloud, we implemented custom 500.jsp for 500 error redirection following approach #1 mentioned here.

We are able to see the plain text added on 500.jsp but facing below issues for customizing the page - 

1. Unable to call/load another AEM page from inside of 500.jsp to fetch all the content and front-end. Our purpose is to utilize the existing 500 AEM page for look and feel.

2. Document status code is showing 200 after this implementation.

Dispatcher-

ErrorDocument 404 /en-us/404-page-path.html
ErrorDocument 500 /en-us/500-page-path.html

code - 

function redirectOnError(){
 response.addHeader("x-aem-error-pass", "true");
 response.sendError(500);//InternalServerError
 throw (new Exception("custom500 called")); // explicitly throwing for 500 testing
}

Kindly guide for any fixes or updates that we can do to rectify 500.jsp issue. Attached is the reference file for 500.jsp

Thanks