If it were me, I'd probably also be trying with -zapwallettx and -rescan to abandon the unconfirmed tx.
That does recover the coins from the unbroadcast tx. But that doesn't change the reason for the tx being rejected (segwit tx on a non-segwit chain) so any coins currently owned by a Datacoin address beginning with 'd' (as opposed to 'D') are effectively now unspendable.
Cheers
Graham
What is no longer sent from the wallet to the exchange? but what to do with the coins on the wallet?