I read this last night and I needed time to collect my thoughts before officially replying. This article does a great job explaining how hard it is to know you are going to become dependent on other people for basic needs before it happens and spend your life watching and waiting for symptoms, and how difficult it is to care for people at home who don't want to admit they need help.
Deciding whether or not to get tested is a monumental, life-changing thing because no matter the result, you are either going to be incapacitated or feeling guilty and caring for sick people. There is no escape from it. You just have to try and make the best life you can in spite of it all. Make friends, go on adventures. hold your family close. Find something to do that will leave a mark of some sort.
Obviously, this hits home for me because I come from a family with Huntington's Disease, and I am the first person to actually take the genetic test in my line in 2018. My odds were the same as this family and my disease is similar to FTD but with added Parkinson's symptoms. My mother did not believe she had the disease, even though she was unable to care for herself until I took the test and told her that I was positive, which meant that she was too. I had to ask her doctor to convince her to get tested so I could try to get some help with her care because nothing I said would get through to her. The denial was so strong she wouldn't even say the word out loud. I talk a lot in my therapy about how I feel like I have the weight of many generations of people not talking about this disease bearing down on me, the first tone to test.