People ought to read the treaty. It gives the US specific rights to use whatever means neccesary to protect the Canal but not to take over the Republic of Panama. It also give us the right to move to the front of the line to transit the Canal in time of emergency.
The Chinese are not in control of the Canal. Period. Not one military commander down here on visits expresses a concern about that. Panama Ports is too busy making money to worry about doing something stupid. they would lose their leases in a heartbeat if the Panamanian workers in the ports found weapons, troops hiding in containers, etc. Laughable at best. Can you imagine being in a container for any amount of time in this heat? Most workers have cell phones. They would all over any troop movements in a heart beat. You can't hide them here.
Logistically, and militarily, the is a world of hurt about 2.5 hours away to take on any threat. Far closer than China.
The article you linked to is from 1999 and is filled with uncertainty. Indeed, there are many here who miss the Americans and our money. However, the fears about the Canal being run into the ground were unfounded.
They inherited a basically sound system of processes and controls. They retained many of the skilled American workers to help the transition. It was sound thinking then and the results are speaking for themselves as a business.
It sounds like you are there.