Wow, Navy... !
I had no idea all this was going on with you.. and I'm so very sorry !
I really hate this for you, and you do seem like you're between the proverbial rock and hard place with your dad's illness and mother's denial.
I truly don't know how to advise you... other than simply doing what needs to be done... there is no way around it. Depressing, to be sure.
And I have a feeling this is why there is such lack of motivation... depression.
Have you anyone there at ALL you can discuss your situation with.. school counselor or therapist/counselor.. to get the emotional support you need?
I'd hate to see you quit now.. you've come so far. And yet, I,too, believe it might be wise to put school on "hold" temporarily until the family situation is resolved.
It does appear you need just a little sunshine in your life right now... a visit away from it all would be refreshing.. perhaps help you to see things more clearly and put them in perspective.. help you to prioritize those demands on your life right now... figure out what's a "must do" and what can wait.. what is truly important and what is merely unwanted stress.
We're here for you, Navy, and feel free to vent, Kid. :kiss
Hope someone else has something more constructive to offer. (((HUGS)))