I picked up a lavender plant cheaply, and am trying to figure out the problem that as become apparent.

When I bought the plant the lower leaves were dry and came off fairly easily. There were some darker leaves--not brown, more like a dark grey hidden in the foliage.
The plant wasn't so root bound the roots were escaping the pot, but when I pulled the plant out I may as well have kept it in, the shape was so perfectly copied! Seems very densely packed with roots all through.

After transplanting, and being possibly a bit over-rough with the roots to try and loosen them up the plant is drooping like its water stressed. The leaves have a very soft feel to them. Some of the leaves are drying up from the tips of the leaves inwards. This is more pronounced on one side of the plant, but its not happening in a distinct area (or all over) like I'd expect a fungal problem, seems to be multiple individual leaves on stems withering, from tip to base, to a dry greyer (darker) green.

I suspect its been in the store since Christmas, I figured I'd take the gamble because it was very cheap, and there's no way I could afford a large lavender plant like this otherwise (and my last one is probably dead, this winter was harsh). I soaked the soil when I brought it home to help fush out anything they may have given it, roughed up the roots and transplanted it, trimmed off some of the more unhappy looking branches, and have been letting it dry.

Is the plant salvageable? What should I do?
Right now I'm keeping it indoors and mostly out of direct light, and am slowly re-introducing it to light through my west facing window a few hours at a time.Soil around the root-ball is very difficult to moisture test because its so dense with roots.

I have some photos of the plant here: https://www.dropbox.com/sh/5krzpuy1j09pky4/xCOmnLkBTj

Thank you