i feel you bro
our dog which was with our family since i was a small boy ( she was 14 years old when she passed away ) also came down with cancer and had a huge 1.5kg lump on her shoulder and she went for opp and managed to remove it , after the opp she came home and was very weak and could not go toilet properly also. i had to syringe feed her everyday along with her medicines. we would give her anything that she wanted to eat and boy she loved home food , as it was her ending days already we just gave her anything she wanted.. i believe new lumps were coming and doctors could not do much as her kidneys were failing also , so meds was not an option any more. few weeks later there was prayers at my place and she passed away peacefully without pain during the prayers. was a very sad occasion
we are lucky that she passed away peacefully. RIP my old friend.