That's a great letter but also sad. I hope things are getting better for you and you have a better understanding of why you felt inadequate.
Just for emphasis you could add another sentence about their money grab. Something like - "Now I feel there is an added pressure and that is to give even more money when I've already tried my best to provide as much as I can."
Since you are writing the letter, think about making it clear to them that you couldn't handle meeting with them to discuss your situation and that you desperately need the time alone to reflect on all that you have had to deal with and to help improve your outlook. You could also add that you would be very grateful that instead of meeting with you, you would greatly appreciate it if they would pray for you. Also that you feel strengthening your relationship with Jehovah through bible reading, prayer and improving the way you interact with your family would be the most beneficial thing to do at this point in time. Tell them that you will let them know if you feel that they can do more for you in the future.
I'm not one to pick on spelling mistakes but given that it is a letter to a group of people you might want to check over it. A few that I noticed were-
Brake down - breakdown, Physiologist, diving - driving, cant- can't