HOnestly? looks like someone took a baseball bat to it?

Theres a chance its spider mites, if so mix a spoon of oil, a tiny drop of dishwash liquid and a litre of water, spray the leaves and stems top and bottom (try not to get on the soil to prevent it getting too wet) , it should kill any spidermites, if there there they are so small you probably wont see them, like tiny specks of dust on the leaves normaly, you can usualy see red on a tissue if you wipe the bottom of the leaves, but not always If you can get neem oil , use a spoon of that in the mix and then it will kill most pests as well. The tips of the leaves look (where they are brown) possibly like a build up of salts from fertiliser or the water, if so you can sort this by a spoon of white vinegar in the next watering, its not a real problem though, bt worth doing The fertiliser realy needs to be a citrus one, as they need a high level of nutrients, and unlike most plants they need a wide range of minor elements to keep them happy, fertilising over the winter if its not outdoors is a good idea (just les often due to less water use) , the fertiliser will be used to build the plant up to flower next year I would have thought they should have flowered, this can be down to fertiliser, but more often due to lack of cold hours in the winter, they need a certain number of hours of winter to make them flower next year, about 600 to 800 for most citrus, you can do without this by shocking the plant by letting it dry out for a long time, but its best to let them have cold hours, below about 16 deg C, but not too cold to kill the plant!

Too much water - probably rainfall amounts . Nothing you can do . This is from U of F : Minneola will develop into a very large tree at maturity and adequate space for development should be provided. Minneola is not strongly self-fruitful and low yields will be experienced if suitable pollenizers are not supplied in close proximity and numbers. Even when pollenizers are supplied and growing conditions are good, Minneolas will sometimes produce disappointingly small crops, the reason for which is not clearly understood. Here is a link that might be useful: Minneola Tangelo

I took the plant completely out of the plastic (very large) pot and examined the roots. The medium had no compaction and was not wet....only slightly damp. Inside, I had been watering only when the top 3 inches felt dry. Maybe I was under watering...but still can't see how that had such a dramatic impact on the tree. There were a lot of roots that were yellowish tan and looked healthy. The roots still had plenty of room. If it were the medium I would think I would have seen stress on the plant prior to bringing it inside. The plant was growing new shoots and had blooms and some small oranges while outside. It was almost instantaneous that it started losing it's leaves once I brought it in. I have racked my brain trying to figure this out. I thought maybe the leaves would show some clues as to why it's dying (which is why I included photos). It was near a large window that received indirect sunlight while inside. Humidity inside is around 52% to 56% depending on the day. I have been so excited at the growth of this orange tree...it breaks my heart to watch it die. Since I made the original post I have taken the tree outside and cut all the dead limbs off and watered thoroughly and put it in a small greenhouse inside my barn directly in front of a south window. It gets direct sunlight now (filtered through the plastic greenhouse sheeting and glass window). It will get sun for most of the entire day....however the temperature will be colder than inside. I didn't feel like I had anything to lose at this point and couldn't possibly make things any worse for the tree. If you have any thoughts or advice, I would appreciate them. Thank you.