Can't purchase coins and redeem codes - Error about EA account appears.

The linked ea account likley uses the swtor email used o create the swtor originally 

if clicking the ea account it likely just shows an ea disabled email now 

if resetting the password on the ea account doesn't restore the account then another ea account exists as you are likely resetting the password for the wrong account 

Calling Swtor support, they can place a new email on that ea account if you do not have access anymore