My sims in dorm rooms

If you move any sims in the same dorm as Cameron Fletcher, he will be a playable sim. The easiest way would be to evict him out. This can be done from Manage World. He will still be a student, but the game will then treat him like any other sim running around in your game. After evicting him, go into build mode, and then delete the extra beds past the number you need for your sims. After moving in your sims you will need to have them claim their beds. The game won't move in any other sims after that.

I think this will work.
1. Go to Manage Worlds, select Tidal Tower, and go to Build mode. Make sure there are exactly 7 beds, and make any other changes you want. Press F1 when you are finished.
2. Select the household of your first sim, enroll in university, and choose Tidal Towers for the residence. Pause the game.
3. Select the household of your second sim, enroll in university, and choose Tidal Towers for the residence. Pause the game.
4. Repeat for your other four students.
5. Send someone to Briny Towers to meet Cameron, make friends with him, and invite him to join the household.

Save the game if everything worked. Exit to the Main Menu without saving if it didn't, so you can try something else.
I haven't had time to actually test this yet. I'll let you know my results once I have.

ETA: I don't think step 5 will work. After testing, I don't think you can ask a sim to join the household if you are living in University Housing. Everything else should work.