I am not sure it’s possible to have transactions paying zero ArbGas price, on testnet or otherwise. When I tried to broadcast such a transaction, the Arbitrum node returned the error - gas price too low.
For comparison, Metamask is showing the same error.
Reading the docs, I found this explanation:
On Ethereum, the gas price paid by a transaction is equal to its gasbid. Arbitrum, by contrast, treats the gasbid as the maximum amount the transaction is willing to pay for gas. The actual price paid is equal to the current Arbitrum ArbGas price, whatever that is, as long as it is less than or equal to the transaction’s gasbid. If the transaction’s gasbid is less than the current Arbitrum gas price, the transaction is dropped and a transaction receipt issued, saying that the transaction’s gasbid was too low.
You mentioned that your Reddit tokens are stuck on Arbitrum testnet. If it’s still the case, I’m happy to send you some ARETH to let you to move your funds out. Alternatively, you can bridge Ropsten Ether to Arbitrum using this bridge.
Going to mark my answer as solution, but if you need further help feel free to reply here.