Interesting machine!
I’ve got the user in a different way and not in the intended one (I believe is the one throught the high port).
Hint to get a shell: DeLorean (if you don’t know what does this mean, you need to invest at least a couple of hours to get some culture 
)
As others have said before me, to get root it’s enough to follow the basic enumeration techniques, don’t overthink.
PM me if you want a hint.