I can't relate to having to testify, but I can definitely relate to having and event coming up that has one's anxiety skyrocketing- I suffer from severe social anxiety, so anytime I have some social event coming up where I might have to do something like serve food, or speak, or even talk to strangers, I can't think of anything else until then, it controls my life- if I let it.
Sounds like you are doing the right things to prepare. May I also suggest:
I hate to sound like a broken record but I find exercise gets rid of that excess nervous energy and helps tremendously. So, before a medical procedure or doctor's appt, or social event. I walk 30 minutes, as briskly as I can every day. If it rains I walk back and forth in my house. It does the trick, at least it tones me down. So, if your doctor says it is okay, it might be worth a try. But you need to stick to it every day and walk faster than a stroll. Also, when I walk I use the time to think positive. "I WILL get through this" " This will NOT defeat me" "I AM a competent person" etc etc. As I walk I also take several deep breaths and feel thankful for my world and being alive. I like to focus on wildlife as I walk and the beauty of the season, too. Anything to derail my Usual Suspects (symptoms). To give my mind a break and wear off that overload of nerves!
Peace to you!