TLDR : how should I prune this tree and/or roots to try to save it since the stems kept dying back from having been started in wood mulch that wouldn’t drain and created root rot? Willing to try anything (can’t take it back to nursery). 

Had this tree just a couple months. I’m in DFW, TX and I’ve only had a few other potted citrus for a year, but they are doing very well. 

This blood orange has been treated the same as the others: outside in daytime when temps were above 50F and inside the garage at night if it dropped below 45. When it was colder than that, I had them in the laundry room under T5 daylight bulbs and would mist the room for humidity once a day. 

About a month after getting it, all the mature leaves fell off and it started blooming all over. I cut off the buds thinking it was just stressed from not fantastic light. Then branches started browning from the tips toward the main branches. I cut them off and checked the pot. Bottom half was soggy and top half was dry. Noticed what looked like some root rot. Repotted in better draining pot and soil after loosening the root ball and cutting off some obviously bad roots. Briefly started improving. It kept some new leaves and stopped browning. The leaves were a not fantastically dark green but not pale.

Then it started losing new leaves and one of the stems turned brown extending down onto a main branch. I pulled it out again and AGAIN, the bottom of the pot was pretty wet, despite not watering in more than 5 days and the top couple of inches being dry and more indications of root rot. So I started digging at the roots more and found wood mulch. The whole growing medium was just soggy rotting wood mulch!  I have used water and my hands to dig out almost all of the mulch and now I’m trying to decide what to do. 

Do I prune it to a stick and prune the roots and hope it revives? Prune just roots? Prune just branches?  It’s now very tall with very few leaves. Willing to try anything. 

It is currently just sitting in a pot without growing medium so roots can dry some after getting all the mulch out

How to save blood orange?