Hello again Pen.
I can't answer your medical question but as far as continuing to fight that would depend on your dad wouldn't it.
While he is determined to give the treatment his all then yes, fight tooth and nail for everything going.
If the time comes when dad says he has had enough then all you can do is respect his wishes and get the hospice/Macmillan involve to make sure he is as painfree and as comfortable as possible.
All you can do is your best and I'm sure you are already doing that.
I hope somebody else comes along to advise you too