I would have left that still in part sun area outdoors, you still have time to revive it. Then do daily spritzing of the entire stem and branches to revive those nodes. Just need to encourage those leaves to come back. I know your area is different than mine and you will have more pronounced winter conditions, but you still have time this Fall, before you bring it back in for winter protection.
I will show you my Calamondin tree, this one to all intents looks dead, growing outdoors but I was away in summer so it suffered big time, got dehydrated, and since our area is no rainfall area during summer, there was nothing for it while we were away. It gets full sun from 11 am to 2pm, and dappled sun the rest of the day. Temps soars high 90F's to triple digits.
31 Aug 2016
But there is still some remaining green part on the lower part of the stem, so I just removed all the dead leaves pruned brittle branches, and continued spritizing the entire plant and watering the root area.
By Oct 2016, some signs of leaf growth finally shows
By November 2016, those leaves continues growing
By 14 Dec 2016
Jun 2017
August 2018, very fully recovered, and right now making buds
So good luck on your plant, it has lots of potential to recover, if you continue it growing indoors right now with such distress and lack of better light, it may continue to suffer. It really takes a big deal of patience for its recovery.
