Sounds like you were using nylon straps/cords and they will streeeeeeach. Like others have said, go with Amsteel or some polyester straps.
Pads tend to shift alot in single layer hammocks, best used in double layer hammocks. Save up and get a UQ, much more comfortable than a pad and it compresses into a small ball unlike a pad which do not compress.
Your tarp measurments sound a little bit on the small size. Might not provide enought coverage during a heavy rain.