Rescue remedy is often best used for stress in its extreme but over the long term its probably best to use some of the other remedies.
Here's a 'recipe' for a calm down spray:
If you get Bach Flower Remedies 'Rescue remedy' and 'Star of Bethlehem' put two drops of each in a 30 mL bottle, top up with filtered/bottled water, (never tap water) put into spray bottle and spray it around him. Spray him 3/4 x per day. Just a light misting is all you need, don't soak him. It will help calm him and the Star of Bethlehem will work on the trauma