It's been a while since taking a look at the project but if my memory serves me correctly:
The 7th thread is triggered by catching up with two of your gangsta rapper friends on the second floor.
The 8th thread is unlocked after completing 7 threads. Its cue can be found in the apartment of a rather conspiracy prone tenant.
The 9th thread is unlocked after completing 5 threads, and its cue is to take your business to a local eatery.
The 10th and final thread is unlocked once all other 9 are completed, and the cue for that one is in your apartment once that requirement is met so it will be hard to miss.
That should be it for threads 7-10, unless you meant a different set of threads.