You could be experiencing a slowing from the attempt to finish the exportation. I would check the resource usage on the system and see if it is still varying (meaning it is still working or if it appears locked out maximum, as you could have consumed all the available resources on the system).
I have never heard of one that size completing correctly, so if it did you are lucky. They are trying to remove the size and ability to upgrade from a qcp limitations in the newer versions but I don't think they have fully perfected it yet. You are correct in that what in the past the absolute largest allowed was 4GB but many times we were finding failures above 2,5GB so we always quoted between 2.5 and 4 GB as the accepted largest sizing and couldn't get Microfocus to give a definitive size but agree that 4GB was the absolute largest and 2.5GB on some systems would choke.
As for the table that carries that information, it all mainly resides in the Projects table within the qcsiteadmin schema. That is what I was looking for when I asked about the status as if it were different I was going to point you there. During a migration the PROJECT_INFO table also holds the migration status information as well (completed or in progress). I hope this information helps.
Hope this helps,