LMills I do hate to hear you are having a trying time for sure. But, take a look at AmyMinty's reply it a pretty good one.
You are spending alot of time in anger over you father and that apears to be a situation that is not going to change. You cannot change him honey, sick or well, the man will remain the same no matter what. There is an old saying "you can lead a horse to the water, but you can't make him drink". That saying applies to your Dad. You cannot bend your Dad to your liking.
The anger is only going to kick your symptoms up somewhat, is it worth that? No its not you have enough to deal with. I know you are young and you are very, very hurt. But this hurt did not just happen over this visit, this hurt has been with you a very long while. At some point you are going to have to learn to let it go. If you don't this will eat you alive this is being seen in your post honey. It can develope into problems later on that you don't need. This attitude towards you has been there a very long time.
You said your family was close growing up. Hhmm how close if you were always treated in this manner. Difference in perceptions perhaps. Sometimes the family thing happens or it doesn't. Its wonderful if a family truly relies on each other but that it not the case all the time.
I am old enough to be your Mom and I have been round HW a few years. One of our biggest discussions we have had here many times is families and friends not understanding our disease. It is all so common for them to turn a deaf ear. My husband had no clue like one of the other posted here. He still doesn't get it. Some people are just that way. Some can nurture while others can't. Some do not want to admit that someone has a disease, they don't know how to cope with a loved having a disease, this list could go on forever, but honey this is an every day thing. This includes spouses, parents, sisters, brothesr and most of all friends. But this is with any chronic disease. For many is lack of education. Some people can read it and still have no clue.
Yes, it would be wonderful if things were different with your Dad but I just don't see this is happening. Instead, focus on the love and support you get from your fiance. He is the main man in your life. Let him be the one willing to help you and be there for you. You can only do this a day at a time. Call the medical providers that you owe, explain your situation to them. Many have charities willing to help out with expenses. Some just simply adjust the bill off.
Get yourself in a better place emotionally, get rid of this anger that is tearing you apart. Peace be with you. Susie