How do you recommend backing up Final Cut Projects with External Data Storage

Hi Everyone, 

Reaching out for advice on the best strategy for a) backing up
b) moving footage around without creating a relinking nightmare. 

Background problem 
- too much footage to fit on one SSD

I am working on a documentary which captures miracles a mission trip to 2 locations in Kenya. 

We have some 3TB of original data which we shot at two locations. At the first location we  got 2TB of footage and the second we had around 1.3 TB. When I tried consolidating all my footage on a large drive, I ended up with the spinning beach ball problem that people here kindly helped me with so I ended up editing the film in 2 parts - with one SSD for the first location, and the second for the second location plus all the FCPX Libraries / projects for both locations. 

As FCPX started generating optimised and render files, my second SSD filled up. 
Creating proxies filled up my second drive - so I am working with original media on the SSD (stored outside the libraries). 

FCPX Libraries 
I am working in 2 libraries - one for each location. 
The footage was not moved into the library - imported but left in place. 
I imported footage into the respective library only. 

I ended up using a slower HDD spinning drive as an overflow location when I generate a ProRes version of the first half of the film, which I bring into the edit of part II. 


Challenge
It is getting tedious to have to render first 25 mins of film and import to second film each time I do an update. 
I would prefer to have all in one library, but I am a little concerned after past spinning beachball problems that having too much footage/too many keywords etc. in one library could get messy, slow or difficult. 

Questions

1) about consolidate projects in one library

Is it wise to consolidate the projects in one library – leaving Data in original folder structures. 

Or is my concern that it might be too much justified?

Will I be fine if I move the project timeline from Location 1 (first half of the film) into the Library/project for Location 2. 

Are you guys working on long films with many TBs in one library with no problem? 

If I put all the projects timelines into one library, will I end up with problems relinking because the original footage is spread across 2 SSDs and one HDD? Or will I be okay provided I have no proxies to relink and all my files have unique names. 

2) when it comes to backups 

How should I back up all this material to avoid a relinking nightmare if I have to restore from that backup. 

1) Should I be using something like Carbon Copy Cloner to backup volumes to own partitions so that the volume names don't change 

2) If I consolidate all the footage into a library on a large HDD, I would have a backup and hopefully have no problems relinking but then I could not restore to a 2TB SSD as it would probably be too big. 

Any thoughts would be helpful. 

Thanks in advance, David