I'm sorry to hear that things are so hard.

The letter sounds like a great idea - sometimes just getting it all out on paper when the panic starts can help a bit. All I can suggest otherwise is to keep relying on the other resources you have (including any relaxation and breathing/grounding techniques you know) as much as possible and try not to be too hard on yourself. You will get through this and hopefully when your T gets back you can work on some new strategies to try and find a way to manage the panic attacks.

There is always us here at PsychCentral too if you need to vent or talk.

Thinking of you