Sounds like you don't even have a broker. Whoops.
Hindsight 20-20, you should have used a freight forwarding service with offices here and in the U.S. instead of a lawyer who probably doesn't have a clue on what had to happen.
A freight Forwarder would have gotten all of your ducks in a row before the container was even loaded in the U.S. so that when it landed, it would have the docs presented to Customs before it got here so all you would have had to do is pay.
Also, that trailer would not have entered the country without paying taxes to DGII on the donated equipment. Doesn't matter if it's "medical missions container to benefit local community hospitals."
Now that the trailer is here, it is accumulating daily charges for storage on the trailer itself, plus rental charges on the chassis along with daily charges on the dock.
How long has the trailer been in the country?