I am so sorry about your diagnosis, and I can't imagine being in your situation with the kids. To answer your question about medical marijuana, there is no "evidence" that it can help slow progression, but there also haven't been any clinical trials to test it. I have a really good article (but very technical) that was written by doctors from University of Washington:
If you want to read the whole article I can send the pdf file via email, but I cannot make it work on the forum.
Good luck getting through the next days and weeks ahead. I know what a punch in the gut this is for you, so stick with this forum as it is a wonderful source of support and information.
My thoughts and prayers are with you, Jo