I am so sorry to read your latest post. I too have been in the exact spot you are. It was such a terrifying time that I now realize I didn't even comprehend. I am still dealing with it to some extent 8 months later.
I hope I am not too straight forward for you. My mother's j-tube plugged (like you mother's) and no longer worked. My mother chose not to have an IV put in and basically only wet her lips and sucked on freezies when she could. We too were told she could hang on for up to 2 weeks due to her age but, she only lasted a few days. My mom's pain was controlled quite well but, the vomitting of bile was a tremendous strain on her weak mind and body.
From what I have been told everyone is different. I truly hope for your mother to be as comfortable as possible.
I will say a little prayer for your mom and you too.