Backstory: ss13 lives with us, BM has mental health issues and lives with her equally mentally ill parents 30 minutes from us. She has visitation eow & Wednesdays.

The most recent problem:
ss13 sending text messages to his "girlfriend" and her best friend that I pushed him into a hornets nest, tried to drown him, poison his food, manipulated the brakes on his dirt bike so he would crash, I beat him severely, E T C......

It's been a hellish few days. 3.5 hours in ss13 therapist's office on Tuesday night, 1.5 hours in our marriage therapists office last night and another session at our marriage therapist tonight.
Ss13 told his therapist that I'M the problem and he feels like I don't care about him. He admitted that he was aware that he was actively doing things to get himself (and bs10mo) removed from our house by dcf at any cost because he doesn't want to live with us anymore. Dh will never send him to live with his mother so that unfortunately is off the table and will remain so.

My task (per our marriage therapist)

I have to figure out a way to change who I am. To me, that means I need to be fake when ss13 is around. ss13's therapist instructed us that the only time we're "allowed" to talk about the problems is in her office, one hour (under normal circumstances) per week. So I guess we all need to fake it for 186 hours a week??

I'll keep a log of the interactions and write up a list of the things I've done for him over the past 5 years. Off the top of my head,

Planning an entire week vacation to Boston in order to have him enrolled in Red Sox Camp.
I was the one that thought of getting him a dirt bike and did the research to get it done.
I made him baseball cupcakes for his birthday for his entire class for 5th and 6th grade.
I bought him Abercrombie clothes so he would fit in for school when he started in an affluent town in our state.
I taught him how to do his own laundry at 8 years old.
I taught him how to set the table at 8 years old.
I taught him how to clean a bathroom at 8 years old.
I got him a subscription for Red Sox magazine and Kid Nation for the past 4 years straight.
I make his lunch for school sometimes.
I help him with laundry in switching from the washer to dryer.
I remind dh to say "please" and "thank you" when he doesn't say it to ss13 in front of ss13.
I did all the research and legwork to get him into a tech school for high school.
I attend every one of his doctor appointments and therapy appointments.
I let him come to the hospital at midnight to meet bs10mos when he was born.
I included him in bs10mos baby book.
I plan things for vacations that we take to keep him occupied/entertained - jet ski's, bicycle riding, snuba, go karts, a pool, etc.
I bring him for donuts when I bring him to school when he misses the bus.
I actually defend his mother when he talks shit about her.
I bought him ALL his gear for his dirt bike.
I have planned every single one of his birthday parties for the past 5 years. We had his 13th at Dave & Buster's.
I buy bs10mos sleepers/outfits that say "little brother" to acknowledge that Noah is his brother.
I get him the groceries he likes.
I put money on his lunch account for school.
I ordered and paid for his $30 yearbook this year.
I got him all his gear when he played baseball and attended every one of his games and practices.
I marched with him in the local Memorial Day parade in 2013 when ss13 was in the marching band at school.
I was a den leader for his cub scouts/boy scouts in 2010/2011.

That def sounds like a list of things someone would do because they DON'T care.

When I'm confronted that "I'm not doing anything to make the changes that are demanded of me" because ss13 says I'm doing nothing different, I'll have written proof about what I'm doing to shine a light on the fact that I in fact am NOT the problem. At that point, I will be holding ss13 accountable for continuing to talk shit about me and maybe we can start exploring the ACTUAL problem which is the fact that his mother has never been and will never be the mother he wants because of her mental illness.

I'm at a loss here. What am I missing? What's your take? Anyone going through something similar?