Hi Kevin,
Thanks for your interest in WooCommerce Tickets.
I can answer your questions.
The way to add a fee would be through WooCommerce. We only have features to setup the tickets and none for fees so I am limited in supporting it.
I did find this plugin that might work:
WooCommerce Product Fees
And yes both regular products and tickets can be in the same cart. Tickets are actually WooCommerce Products, just a special kind.
Let me know if you have any follow up questions.
Thanks