Kaptinlin Themes Support

Hi, I am sorry to bother you, but i want to achieve 2 things at aurove.com:

1) Show in my portfolio my website designs, but i want to display the full size image, at 900 to 980 px wide (depends on the design). How can i set up the lightbox to show the full image without affecting the other portfolio categories?

2) I want to set an expiry date in the HTTP headers for static resources because i have experienced a low performance on the site since i´ve made my blog public. I have tried a couple of things myself (but i am just a designer, i have 0 coding knowledge) like:
a) Set Expire Headers In htaccess following this guide: http://www.paulund.co.uk/set-expire-headers-in-htaccess with no success. I have made the changes to all my .htaccess files in the server.
b) Using WP Super Cache plugin (after deleting the changes to my .htaccess files) which is currently installed.
None of these 2 things seems to work. May you help me with this issue? I am using https://developers.google.com/pagespeed/ to test the performance.

Thank you for your time!