First, thanks for your purchase.
For the first question:
The shipping info tab is additional product tab. You can change that on admin->theme options->single product->filter tabs.
If you want to change the "Shipping info" title, please change the additional tab title value.
And to change the tab content, please replace the tab content html block.
For the second question:
On which page did you get that error? Could you explain in detail again with screenshot images?
Then, we'll check in detail and provide solution quickly.
Best Regards, C-Themes