Filing an amended 2015 return and don't know ow to answer some questions that seem forced by the program. Form 4868, "Line 7 must be entered." Do I just ignore them?

[Critter]

Ignore anything to do with the extension form as it is too late to file one now. 

If you made a payment with an extension filed back in 2016 then ...

To enter, change or delete a payment made with an extension request (Federal, State, Local) -

• Click on Federal Taxes (Personal using Home and Business)
• Click on Deductions and Credits
• Click on I'll choose what I work on (if shown)
• Scroll down to Estimates and Other Taxes Paid
• On Other Income Taxes, click on the start or update button

On the next screen select the type of extension payment made and click on the start or update button

The payment made with the federal extension request will be included on your tax return as a tax payment, Form 1040 Line 70, Form 1040A Line 46.

Or enter federal extension payment in the Search box located in the upper right of the program screen.  Click on Jump to federal extension payment