It is absolutely not necessary for you to take the numbers. Godd job on not collecting more pressure. You can always get those numbers later on. They will understand your decision.
Take your time for the group-work. If something works for you just be persistant on it.
I was weirded out by my group for their spirituality focused way of doing things but eventually found a way to appreciate what they did for me without needing to leave my safe atheist spot.
Just try to figure out what they can do for you specifically as you just observe the rest without engaging in everything.
It does take time and the first few meetings are (at least in my case) weird and confusing. Just take your time and leave if there is nothing you can get out of those meetings.
Your writing is relatively structured and your thoughts seem to be reasonable for the many variables that must fly through your head right now.
Sex or pornography is often used to releave some stressors. I think you know yourself where it gets problematic. Maybe you want to suggest to you partner to please each other.

Maybe you want to write on a piece of paper "I will stay strong" and read that out to you loud before going on the radio. Whenever i found my hand squeezing in my pocket because bad feelings overwhelmed me, i also found notes i wrote to myself for these situations. You can choose what you want to be reading ahead of the situation. Honestly you probably know yourself best what the situation will be like so you might want to change the words above.
Is your partner attending therapy? Unfortunately THC will tear you apart if you consume it while your depressed. You partner needs to stop smoking cannabis as long as she has depression!!! It gave me the worst phsychosis you can think of. This drug is severely misunderstood by most people. Please tell her she should not underestimate the strong sublime effects she is probably not going to realise as long as she keeps smoking. Her assuming cannabis would help against depression already shows that she has absolutely no clue what cannabis can help for and what not.
Sorry for getting into that like this but it always makes me angry hearing the cannabis misconceptions advocated by interests that do not care about the health of people and exploit their lack of knowledge and need for help.

Your partner is probably expressing the lack of trust in the situation (when you were the most honest towards her) yesterday night also partly because it is a "new" or "intense" behaviour you are showing towards her. Of course she also expresses it because you did stuff in the past that makes it harder to trust you. Nevertheless there are strategies to overcome this. I cannot tell you on here but i think your therapist will.
Honestly you did mention a lot by now that aggregated makes it hard to sort out where cause and effect lies. Obviously the depression of your partner doesent make it easier for you.
Is she living with you in the hostile shared apartment?
Do you know of any serious problems your partner is struggeling with (especially those that affect you directly)? (other than cannabis and depression - which btw correlates)
What genre is your music about?
hope to hear from you again
ps: maybe you want to prepare for your therapy session as there is a lot to talk about. i find it helpful to write stuff down and outline as it make the conversation more structured and fulfilling