Help with IFERROR Formula blanks

Hey guys i was wondering if you could help me with the formulas in column G and Column I of the included sample sheet.

What i want to do is if there is no date in the "Promise Date" column (D) then i want it to be blank unless there is a date in the "Ship Date" column (E) in which case i want it to show "Not Promised". This is to avoid it showing Not Promised when the cell is not populated which is what it is doing now. There are other criteria in play as well but i can't add another without it giving me an error stating that im doing to many functions.

I've added a few mockup dates so you can see the different things it is currently doing and what the other criteria do. This is all so that in columns M and N it calculates the percent on time for both the delivery and our promise.

Thanks alot for your help!