Visual embedding causes errors

I just migrated G1 to G2 and it all went well.

Until I decided to embed the gallery into our website's visual layout.

For that I used the gallery2embedded.php method.

Now there are 2 problems:

- Mod_rewrite module does not produce results any more.
- In some cases when clicking on a link I get the error: Warning: Cannot modify header information - headers already sent by (output started at /var/www/vhosts/sanp-staging/html/includes/tags/head1.php:13) in /var/www/vhosts/sanp-staging/html/gallery/modules/core/classes/GalleryPhpVm.class on line 124

What am I missing? Why is it so hard to embed this without having to modify smarty templates?

Please help.