Everything Taking Forever After Mavericks Disaster

Question

VERY long story short, I tried to update to Mavericks on my iMac -> bad unrepairable disk -> reinstalled new ML OS on an erased drive->Used Migration Assistant to move files from my 3TB Time Capsule (previous generation) backup to my iMac. Everything that was supposed to be there as of October 27th (my last TC backup) was there. Whew.
I backup three devices to TC with my iMac having about 900GB to back up but the TC disk only had 25.6GB of 3TB free. TC connected directly by Ethernet cable to iMac.
Didn't know what to do since I changed the name of the iMac, but got lots of errors (e.g. can't find backup, etc.) but eventually I changed it back to original name and clicked Start Backup (it said Last Backup: None). After churning around for hours and hours, it showed Last Backup: August 12, 2012 and said there was about 11 GB to back up. After many more hours it finally backed up about 1GB of that 11GB.
Next time I looked, it was not backing up anymore, but "Cleaning up old backups...". This went on about 12 hours, and I clicked the X stop button and put the iMac to sleep.
This morning, the oldest backup is January 4, 2013, clicked Backup Now -> "Preparing for backup" -> after an hour, back to "Cleaning up old backups.."
I'm getting pretty fed up after spending a couple of days watching it churn preparing and cleaning, and I haven't got a new backup yet. At this point I don't care about old versions of my files but since the effort was made I would tend to want to keep the versions - just the last month's versions would be OK.
Should I persist letting TC churn for days and trust it to do the right thing, or should I somehow get rid of the iMac backup and just start from scratch (for the iMac, I don't want to start from scratch from the other devices - which tooks weeks to back up via Wireless)?
Would it be any faster to just start over, and how do I do that for just one device (my iMac)?
Thanks for any wisdom.

Answer 1

After 16 hours the "Cleaning up old backups..." stopped and it started backing up ~900gb, which is the entire amout of disk space used by the OS and my documents on my 2TB iMac drive. At least 400gb of that are photos and documents that were not touched except perhaps when they were migrated to the drive using Migration Assistant.
The Time Capsule 3TB hard drive is full (one of my other devices only has two weeks of backup in the last year now), so I'm thinking to start fresh.