Boot Partition suddenly inaccessible

Question

I've run into quite a problem - my Mac (mid 2015 21.5" 4k iMac, running Mojave) cant find my boot partition (disk0s2). I've made some headway, it previously just showed it as FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF.

I now have disk0s2 back, recognised as APFS, but it isnt in a container so my Mac can't find a way to use it. It's also now 883.2 GB rather than the 960 GB it was before (any explanation for that would be helpful).

I dont think I have deleted the files associated with the container, my reason for this is that when I type in diskutil list, after it listing the contents of disk0 and disk1, it shows disk2 to disk17, each with no 'type' and all called 'untitled', each of them being different sizes but none more than 6.3 MB - I think these are the contents of what was previously an APFS container.

Prior to this my primary drive was just in a container called 'Container 1'.

I no longer have the ability to paste anything from Terminal here because my fresh install of macOS Sierra diappeared at some point (I'm installing it onto a usb drive right now). When I type gpt -r show disk0 theres an entry with no index number that has the size 226802864 (maybe thats the lost partition). there are a couple others but none that size. I posted more detail here: https://discussions.apple.com/thread/8584377

I've installed macOS Sierra onto a USB, this is what disutil list gives me:

(disk2 to disk17 are no longer visible, maybe because this wasn't done in recovery mode)

and this is what sudo gpt -r show disk0 gives me:

I've entered sudo dd if=/dev/disk0 bs=512 count=1 skip=409640 | hexdump -Cv and this is the result:

It was pointed out that this might be a duplicate of the question found here: macOS partition startup Volume type FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF but I followed the steps in that guide and that's where I am now. diskutil list:

sudo gpt -r show disk0:

diskutil verifyVolume disk0s2

So, while I've followed the guide, disk0s2 was 960GB and in a container, but isnt anymore. I cant access that disk at all, although the data is intact. I've been informed that Sierra was pre-APFS so I'm going to be updating the OS on my thumb-drive.

I'm about to install Mojave to read the APFS disk, but until then these are the files that iBoysoft Data Recovery has found, in case anything useful can be gleaned from them:

I've installed mojave on a USB drive, now maybe I can do something with APFS, any suggestions would be appreciated.

Here are my current 'diskutil list' and 'sudo gpt -r show disk0' readings:

I can't comment yet but if you give any suggestions I'll update my question, thank you.