WordPress.org

How can I exclude my page with links from masking?

Now you just put URLS you need to the exclusion list, or disable masking for concrete post - and everything's OK!!!

How can I mask links in custom field?

You will have to add just a line in theme code where you output custom field data.
To add same preprocessing for data as for comment text, use
$metadata=apply_filters('comment_text',$metadata);
For example, if you use some kind of metadata, it should look like this:
$metadata = get_post_meta($id, 'MetaTagName', true);// get data from wordpress database
$metadata=apply_filters('comment_text',$metadata);// add this line of code for preprocessing field value
echo $metadata;//output preprocessed field value

That's if you want to mask links in custom field like in comments text. Use "the_content" instead of "comment_text" if you want to use the same masking policy as for post text.