Can you call your or wife's employers EAP program? You get some free social work expert help, which who knows, can sometimes alert you to some funding or support that might do the trick.
You should be entitled to tax refunds for anything you pay for childcare, including a private nanny, and there are some nannies who are trained or trainable for autistic children's needs.
I read _Now I See the Moon_2011, Elaine Hall. This book more than any other opened my eyes to parenting and emotions of someone who loves a child with autism. I highly recommend this book for many reasons.
Once you learn each of these life skills of coping with a special needs child, you will be a better person and you will not feel as depressed, I hope, because you will have the pride of knowing what you have been capable of doing for someone else (who really did need you).
You're sleep deprived, and you can't solve many complex puzzles that way.
Ideally, you could teach music lessons by appointment in students' own homes (when their parent or guardian is home) at times that don't interfere with your stepdaughter's AM schedule and your time with your new wife. Both are important. Then maybe work from home or find a boss who is more flexible.
