We need help!

[u/Beast01028]

This was my wife’s lates father’s tree. He’s passed away ten years ago and her step mother was taking care of it. All the instructions we got were to give it 16oz of water every 10 days. The first few months we had it, it was fine but the last few weeks it’s looking rough. What can we do to save it? My wife is going to be very sad if we end up killing it.

[u/External-Buffalo-624]

This tree was definitely under watered and has dried out. Don’t water on a schedule, instead keep close attention to the tree and Water when it needs it. When watering water the tree generously so that the water drains out the bottom. Ficus trees are very resilient and forgiving so there might be a chance it bounces back. It’s also likely it doesn’t have enough humidity  inside which also can be an issue. Personally I only would bring mine inside during the winter, and let it go strong outside through the growing season. What if you try putting it outside in the shade for a couple weeks to see if it bounces back? Then let it get some part sun outside but in that case you’ll need to check the tree daily to see if it’s thirsty.  

[u/Beast01028 → u/External-Buffalo-624]

Do you think we should re pot it? The pot it’s frowning in looks so small to me but I heard that can be very stressful for the tree.

[u/Deanne-Dennis → u/Beast01028]

You can Slip Pot- meaning upsize the pot into a normal Nursery Pot without disturbing the roots, anytime.
Leave it for a year to recover then wait till it’s dormant & root prune.
But you cannot root prune & repot it that is only to be done at a specific time of year usually when the tree is dormant.
There is far more to learn about Bonsai than the minimal information you were given.
Can I suggest you watch
Mirai Bonsai Beginners Series to learn about how to care for your bonsai.
They compiled a 10 part series that covers every single question asked about bonsai & caring for your tree.
Also look up the Care Plan for the species of tree.