Those cracks don't really have to do with the jack even though they are lined up with it... it all has to do with the stress concentration at the end of the weld on the tongue, the cracks on both sides line up with the end of the welds... It sucks but if you have a welder not a big deal, it looks like it's been around the block for a while, it happens... At least he obviously had tongue weight so you still have a trailer and neighbor! trailer sway sucks and can get bad... I've literally been towing, couldn't move the load forward and bought tongue weight...