IF failing to decrypt data in TWRP, can system be restored without loss of 'data' partition?

Greetings! I installed iodeOS onto a Note 7 for a friend’s dad and he got back to me over a year later asking me to get it back in working order. It’s failing to boot and hangs on the splash screen of the OS. It has TWRP installed as the recovery and it asks for a password to decrypt the data. I’ve tried the passwords he’s given me, but I wanted to make sure of a few things as I’m not entirely familiar with iodeOS myself.

A) Is TWRP even able to decrypt the data?
B) Would the decrypt password be the same password as the initial login?
C) From what I’ve read so far, am I correct thinking that in order to restore the system the data partition needs to be reformatted?

When I enter a password, I’ve given the following

E:Decrypt took too long, killing process
Failed to decrypt data.
Unable to decrypt with default password. You may need to perform a Format Data.
Updating partition details…
…done
Unable to mount storage

When I tried to wipe the Cache & Dalvik Cache:

Full SELinux support is present.
Unable to mount /data/media/TWRP/.twrps
Failed to wipe dalvik
Updating partition details…
…done
Unable to mount storage

Really not sure what this guy did, but he seems to have really messed something up here. =/