Hi Russell!
Thanks for getting in touch with us!
First, please let me note that we are fairly limited in how much support we can give for custom development questions like that.
That said, we always like helping out and at least point users into the right direction as much possible.
The tribe_get_full_address() function is located at /wp-content/plugins/the-events-calendar/src/functions/template-tags/venue.php file in line 204.
You can use the tribe_get_full_address filter available to customize the output of that function.
for the website link target there is also a filter available in that same file to customize it. It’s the tribe_get_venue_website_link_target filter in line 648
Hope that helps! 🙂
Best.
Victor