If I've learnt a few things from dealing with a loved one in the same situation, it's the following: take a break whenever you feel you need it, don't take *** from someone who is ill-it's not your fault that they're ill & finally, look out for yourself; your health and mental wellbeing is just as, if not more important than your loved one. If you end up burning out because you're dedicating all your energy to your loved one, it's not going to do anyone any good. 
 

if you ever need to talk, rant or cry, do reach out to anyone - online or in your friends/colleagues/family when you need help, because people can be super lovely when they need to be and this experience has enlightened me on how many people do actually care.

Thank you so so much for this! My partner has really bad personality changes too one minute he's fine the next he's horrible! It's like jeckle and Hyde!! I really hope your dad gets through this okay and I hope yourself and family get through it all too it's the worst news ever and I can't imagine a parent of mine going through it same for you if you ever want to chat I'm here! Thank you so much again XX 

One of the things that has been reassuring-and is a wonderful group of people-is the 'cancer community' on social media. Social media can be a horrible place but there are some really good eggs on it too! Deborah James (@bowelbabe) and Kris Hallenga are among two of the people that I follow online, both of them have been given various awful diagnoses with their cancer, including being told that it is late stage and incurable-but, they're both surviving and thriving by all accounts, years after diagnosis. I also recommend you check out the podcast that Deborah James and Lauren Mahon do -it's on spotify- it's called 'You,Me and the Big C'. I'm not exactly a podcast 'person' but it has been an amazing support and also really interesting to listen to. It covers all aspects of having cancer and they often invite guests on it to talk about their experience of cancer.  It's really reassuring knowing that there are other people going through a similiar experience.