Hello,

1) Let me explain again. Let’s take an example you are using English for the US language on your site, and the language files are en_US.po and en_US.mo, Now rename those files as woodmart-en_US.po and woodmart-en_US.mo and place those language files under wp-content/languages/themes It will not be overridden again whenever you will update the Theme same as for other languages you are using.

2) We suggest you to use this plugin to add any code to the header or footer https://wordpress.org/plugins/insert-headers-and-footers/

Best Regards.