I took the big building pad in the project and just did the following
1)Changed the Mid point of the middle south side as the start station - used Break and Join to do that.
2) Used your sideslope definition to create the sideslope
3) Built a surface from the Sideslope lines and the source line (Optional)
4) Lastly you should change the property ofthe surface "Adjust Flat Triangles to "Yes" - that will force the sharp corners - you had it set to No and that allows flat triangles to form at the "Internal Corners which you dont want.
5) I used a random sampling distance eg 2.18 so that it is less likely to hit a corner spot on (Tolerance issue wehave addressed in next release
It looks like this in a few seconds.

The others would follow suit I think as shown below

This was zero editing, zero trimming and extending, no corners to close using the above steps only. The only change I had to make on some sideslopes was the Interval computation because I was hitting the Tolerance issue on some of the pads with the tolerance I was using.
This took me less than 5 mins to get this far
The Surface properties has a lot to do with the success here.
Alan