Fleet

I'd recommend investing in Hound's tooth. It's still the best ship out there, and will make a lot of things easier, ship-wise. You could probably 3* it with your current fleet and a hounds tooth. Run Silencer, HT, ITF. For reinforcements I'd go with TIE Advanced, Scimitar, and then either Ahsoka or Slave 1. Also, unlike squad battles, you can get 3* with one defeated ship.
One more thing that may help is unlocking Chimaera. It's a generally better ship than Executrix, especially for campaign, since it can heal/control TM.