50 or 30 amp

Surge protectors are a good idea and offer protection from lightning strikes but won't help for the kind of overcurrent fault we're discussing here. 

On the question of whether the arc fault breakers are better now, I'm not sure but it looks like we're on the 3rd or 4th generation already. The original type from 1999 aren't even allowed anymore. The newer ones are intended to detect series arcs (like from a loose connection) as well as the kind of parallel line to line and line to ground arcs we've been discussing. So they are still adding features and sorting the technology out. 

The 30A CB in the pod has no way to know if there is a fault upstream from it. It only knows about load and fault currents flowing through it heading downstream. If the fault is in the cable or in the trailer connector or in the conductors between the trailer connector and the pod breaker panel then the conductors from the pedestal to the fault will see the total of the fault current plus the load currents of anything you have on in the trailer. The trailer cb will see the load currents only. If the load currents are 30A or less and the combined fault and load currents exceed 30A but are less than 50A then neither the park's 50A nor the pod's 30A breaker will trip, but the 30A rated conductors up to the fault location will overheat. That is where the fire risk lies.