Hi Enre,
To begin with I would like to ask if you have already run the Initial Full load using the report 'CRM_MKTTG_TREX_UPDATE' . I am not completely sure about the size of all the table that are a part of your infoset. However with table sizes of 6 million and 640 million should be completely replicated to TREX is less than a week (even lesser. if you are in latest support pack then may be 3 days).
My next check would be the TREX version and the SAP CRM sp level. SAP has released a few notes to improve performance on the TREX upload job. If you are in CRM 7.0 Ehp 1 SP 05 or less then check out for the notes apply them to imrpove performance.
Thanks,
Hemanth