You could try the following custom filters to get the file size and dimensions, and print them to the results contents. Place it into the functions.php file in your active theme directory:
Make sure to change the $file_field variable value to the custom field name you store the files in. This works on my test environments, but it may depend on how ACF is configured.
The ligthbox is not possible without a larger amount of customizations, and it very much depends on your specification and needs.Best,
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