Are you merging these leads manually? Marketo should not automatically merge the two records just because there are two form fill outs in the same browser.
The suspension will persist for 24 hours after a spam-related bounce regardless of any changes to the record. Just send again 24 hours after the suspension.
Can you show us a screenshot? Once a lead is Email Suspended, this condition persists on the record after 24 hours EVEN THOUGH Marketo will send to it as long as Email Invalid=F and Unsub=F