You did a beautiful job! With all of that info and photos, I now think the problem is that the roots are waterlogged and starved for oxygen because there is no drainage. Repot with fresh soil. I wouldn't go into a bigger pot, especially going into winter. If there is a disproportionate amount of soil to roots, the soil stays wet too long and you risk rot again. Your peat-free soil mix sounds like it drains well. When you water, put the pot in the kitchen basin, slowly fully saturate the soil, then let it drain completely before setting it onto a saucer on your shelf. (Saucer to protect surface)
Unless Tiffany responds and says otherwise, I suggest clipping each stem by about half when you repot. Hopefully you'll see new growth soon and can clean out dead bits later. Your potting mix has nutrients in it. Start fertilizing with an all purpose liquid in about six weeks.
