*My* suggestion:

Start cutting at the top, or ends of the branches, and Don't Stop Until You Find Live Tissue. Toss your cuttings aside for defoliation. Pluck any viable leaves and put them in dry soil to start new plants. You *must* find out how extensive the problem is from the top first. Once you have a salvageable plant remaining, take it out of its soil and completely wash all the dirt from it.

From here I will copy/paste directions I gave to another poster re: her c. ovata:

"Unpot your plant and completely wash the soil off with spray from the hose. **Note if there is a ball of peat around the root-ball** Check for any dead, mushy or grey roots and remove those with a sharp, sterilized knife. Sprinkle any cuts with cinnamon and set it in a dry, shady spot for a few days to allow the cuts to callus over. Prepare some proper succulent mix. *No Peat* There are as many mixes as their are succulent growers. I use 50/50 organic potting soil and haydite but turface, decomposed granite or even perlite will also work...but *No Peat*...did I say that already?

Peat becomes hydrophobic when dry and almost impossible to rehydrate. Since succulents need to dry out between waterings, it is a recipe for disaster. Oust it! Since most commercial growers use peat, it is highly possible that after the first time you allowed your plant to dry between waterings the peat was dried out and has never rehydrated whereby your plant has not had a good drink since you brought it home. Water will roll down the sides of the pot and out the bottom, never giving the roots a chance at it. This is also why you cannot remove a root-ball from a nursery pot and plop into a new pot, adding fast-draining dirt around it...that only exacerbates the problem.

(edit: Peat also stays too wet too long, thereby rotting the roots off your plant)

Once your plant is re-potted, you can resume a normal watering schedule as it has (hopefully still will have) a nice root system. Don't bother to measure the amount of water you are giving. Instead, drench the container until water runs from the bottom...this time it should drain almost instantly from the soil surface and will trickle thru the "soil proper". You can now confidently (and properly) allow the soil to dry between waterings with no worries."

(edit: If you do not have a good root system remaining...Remember, the fewer roots, the less water the plant can consume. Water only as needed; when the surface soil is dry to at least one inch, not because a week has passed )

May I additionally note that the combination of low light and weekly waterings is deadly to C. ovata. They thrive in bright light and drench/dry watering.

Also, until I saw definitive growth, I would place this plant outside in *bright shade or morning sun only* so that it has a chance to recover itself.

HTH! Losing those family heirlooms is painful. Jo