I am sorry you have had such terrible experiences. For the hair loss - have you been tested for anemia? Given your GI Tract issues, I have heard a link to anemia as a result (for some not all).

A common remedy (and I am not a doctor) that has helped me in the past with GI issues is a powdered herb called "Slippery elm" - I think at some pharmacies / grocery stores you can buy slippery elm lozenges. You can also make your own - buy powdered slippery elm from a reputable company (Frontier Coop or Mountain Rose Herbs) and mix with Honey - into a pastry texture and roll into balls. You can then suck on one slowly as long as possible - maybe twenty minutes. My experience is that is soothes the GI track.

If your GI Doctor is not able to assist, then you might want to consider very simple remedies on your own related to meditation, acupuncture or reiki/qi gong type practice. what can happen is slow activities increase body awareness and your mind/body works more in coordination.

There is a great book called "The Body Keeps Score" -- basically everything you tell yourself, your body believes. It is not "magical thinking" it is saying once a problem is identified, you are in a position to be compassionate and choose ways to address symptoms better and/or find high tech solutions. Think of all the ways the GI is still operating and doing so much for you - I'm sorry if this sounds overly woo-woo. It sounds like you can have a very positive mindset given your parents living long, you are working and active walker. Best of luck to you and I'm sorry for the situation you are in currently.