Help! Dwarf Orange Tree in Dire Trouble.

I bought it online a few weeks ago and it arrived beautifully healthy, albeit a few spots of fluff here and there. It was also fat with fruit. I watered it a few days later when it felt very dry and again after that (we've had some scorching weather and it sits on the sunniest window ledge) the leaves began to wilt and then very quickly it started to deteriorate and is in a desperate condition.
I've tried leaving it in the darker kitchen for a few days in case it was scorched. Within the first few hours the leaves began to open up, but by the next day they were dried out, crumbling and completely curled. I put it outside and it curled and dried to the extreme. Yesterday it was watered when it came inside and today it's back in the garden in the sunshine. I'm really worried about this plant. It's so dry I can barely touch the leaves without them crumbling. 

- No signs of root rot. 
- Soil is damp but not soaking. I can feel there's a little water in there but the roots at the bottom are almost dry. 
- It's now outside sitting in the sunshine and goes into the darker, cooler kitchen later in the day. 

Any idea if I can save it?