so sorry to hear about your Dads diagnosis... I agree with many here that each B Tumour affects every differently - but the advice you have had seems pretty accurate.
My cousin lost her 6ys old to one a few years ago and I have to say it was the darkest time of my life. Hers was inoperable and they decided against RT since it wouldnt actually cure or eradicate and only prolong the inevitable.
She first lost movement in one arm, then the other, and found it hard to walk. Speech became slurred. She also unfortunately threw up a lot and became somtimes aggressive (due to frustration too I think). She did suffer with heaqdaches a lot - but never complained. Eventually she stopped eating other than jelly and ice cubes and the Macmillan nurse alerted her family when the time had come. Her passing on was peaceful...
Its important that your dad tells the doctors or someone when his medication is not enough - so if he is in pain to say so and they can make him more comfortable.
I'm afraid it doesnt sound like you have long... which from his persepective may be a small blessing in that he wont suffer on for many many months.
Thoughts with you!