Hi. Could you please help me ID my succulent and know how to care for it? It's not looking good and I am sad about it.

I am new to succulents. I received a cutting of what I think is Crassula dubia or Crassula arborescens in Oct '15.

Edit: Oh, I think it's a paddle plant. A Kalanchoe thyrsiflora?

First 2 pics: the succulent 3 mos ago.

Second 2 pics: pics from today (2/16) (Doesn't it look sad?). I noticed the top set of flaps have turned vertical since moving it to this new sunny, warm location, whereas, they were open and out before. Is it going to get sunburnt?

Over the course of the last month or two, the bottom leaves of this plant have slowly wilted and can be removed very easily. When I remove them, they look just slightly dry and shriveled. I was keeping this plant in a window with cold temperatures during December and January. I am wondering if that was my mistake. So, yesterday, I watered it and moved it to a morning sunny, warm room. Interestingly, the top surface still felt moist this morning, so I am not sure if I am over or under watering it. I was waiting until the soil felt dry 2" down but maybe it just stayed too moist after watering because of the lower temperature.

I am wondering if I should just cut the top healthy part and try propagating it again.

Or, do I need to get it out of it's soil and replant it in some non-gnat dryer succulent soil?

P.S. The white powder is diatomaceous earth. I bought some Black Gold succulent soil that I planted this succulent and some of it's former neighbors in. The soil seemed to have fungus gnats so the DE is just one of the steps I've taken to treat it.

Thank you so much for sharing your knowledge and your time.