I believe that by handing off your pony to the out of air DM you would have defused the situation, that is why I like to side sling mine as it is very easy to hand off.
Assuming that the pony was filled, the valve was turned on, etc. Alternatively if there was a previously undetected problem with the pony it could have escalated the situation.
Sounds like the OP responded appropriately and handled the situation. Introducing additional task loading to the situation could have just complicated things further.