I have had major mental health issues for over 22 years. 10 years ago I was diagnosed with bipolar, and then many other options until this last year, when trauma was introduced. It made a HUGE difference. The information given to me was much more helpful and sensitive, and I was able to understand WHY I was reacting the way I did, and that it was a normal response, given my experiences. This helped me make large steps toward calming myself down, and treating myself with more compassion helped to make the anxiety last much less time.
I was diagnosed with DDNOS, similar to DID, as I had different alters that would take over depending on my mood. When I was scared I reverted to acting like a child again, when I was angry, I would think of the world in different ways, and when I was calm and zen, it was like I didn't have any issues at all. I always thought this was how other people experienced life, and that I just couldn't handle things as well. After working with a trauma therapist for a few months, i was able to understand that these different moods were controlled by alters who came out because I wouldn't let myself admit I was feeling angry, sad, scared, etc.
I am doing much better and switching much less, but it isn't because I'm controlling the alters. They would hate it, absoultely hate it, if I tried. Instead I work with them, listen to their thoughts and emotions and try and give them what they need (which is really what I need as a whole anyway), and give them the validation they need. If I start to feel the scared child become really strong, I know that I am starting to be scared, but not allowing myself to admit it. I will say, "I'm scared because [the person sitting next to me in the waiting room is much too close]" to use an example from this week. I will validate it by saying [it makes sense that I'm upset because my personal boundaries were not respected growing up, and this reminds me of some scary situations]. I can then reassure the part that [this isn't the same person, and they are not going to hurt us. Even if they wanted to, we are in a big group of people who wouldn't let that happen]. In this situation I was still feeling scared, so I listened to the part and moved seats so that she wasn't being triggered anymore. Somestimes it's as simple as acknowledging the emotions, sometimes it is a lot more complicated.
What you talk about, with the bangs reminding you of gunshots, reminds me a lot of trauma responses. This is what makes me think that if you could find someone who specializes in trauma, they might be able to help you more than a general mental health support would. Trauma creates chemical changes in the brain, which cause different throught processes, reactions, etc. It's like if you have a cold, you go to your general doctor. However, if you're having issues with something else that is causing symptoms that seem like a cold, like an autoimune disease, your general doctor would be little help, you'd be much better understood if you saw a specialist. If you have anxiety symptoms and a general anxiety approach isn't working, they could be caused by something that needs a different approach.

Sorry this is soo long. I will stop rambling now. Hope you are feeling better. The colours on the white board sound like a brilliant plan to figure out how your system works.
xoxo
IJ