Question 1:
On the list, create a "When an item is created" Flow, and then just use the "Update Item" on the ID from the trigger, and change the column you want to "Response Received".
Question 2:
Use the "Schedule" trigger, to run once daily.
Use the "Get Items" action to look at the list, and use the Filter Query to look at anything in the column that is null using the Status eq null input.
Use a Filter Array to get only those items where the DueDate is equal to "Today" using the formatDateTime(utcNow(),'yyyy-MM-dd') expression.
Use a condition to identify if we got any items returned in that filter array by using the length() expression.
In the "No" side, do nothing. The flow will end if no items were returned that were both missing the status and due today.
In the "Yes" side, create your email, and input the "To" to whomever you want from your Trigger's dynamic content.
It will turn into an Apply To Each - which is what you want - just in case there is more than one outcome.
The whole flow ends up looking like this:
