I did a search for the genus, and all google could thrown up was your post
I'm loathed to give up on any living thing so I would show some tough love and hard-prune the roots and be ready for top growth to die back until the topgrowth can cope with the root system (and vice versa) and stick it in a sheltered spot outside.
All of that might be too much of a shock for the tree so mebbe just put it outside for a while (perfect time of year) and then tackle the roots.
Keep the feeding and watering up.
And don't hit me if it gives up the ghost.
Orrrr... plant it outside and start afresh with a new tree?
Did you taste the fruits?
Could be an olive tree - so - a hot, sheltered and sunny spot would do the trick.