Hello Jim,
Thank you for reaching out to our technical support forum. I’m sorry to hear about the trouble you’re experiencing. 
Sorry, the external link does not work when you turn on Scroll To option. Because on data-scroll-to attribute is added to the anchor tag. I will talk to the developer team to fix this. 
When you turn on Scroll To and set Scroll Offset, this tells the scroller how much it should scroll when clicked. For example, if you set scroll offset 100, there will be 100px space on top of every section. Suppose, you have 5 sections with internal links. Now, if you go to third section by clicking the menu item, it will take you to the third section but will keep 100px on the top. If you set 200 Scroll Offset, then it will keep 200px space on the top of each section when clicked.  
I hope that I could make you undestand how it works. Let me know if you require further assistance. 
Best regards