Made it a clicky link...
CLICKY LINKOne SHOULD have seen that coming from the start, bad idea to use an OFFSET "adapter" to ANYTHING carrying a heavy load like a tongue jack. Has failure written all over it, the load has to go somewhere typically to the weakest part in the whole chain.
For what it is worth, you could have simply made your own by drilling a hole into the bottom of your jack and used a piece of pipe of a larger diameter which would slide over the tongue jack tube. Then a long bolt through both pieces.
However, EXTENDING the jack tube length more than a few inches will put more strain on the jack than what it was designed for so I would not recommend extending the length.