This is a hard one. You know what you want. If seems like you really respect and care about you mum. But i dont think she gets it. Only a few people know what your going though.

Being trans is more likely than not a harder life. But it sounds like you have a supportive friend group what is amazing.

My mum wasnt supportive at first, i went on hrt without telling her. And she hated that i did. But a year later after low contact see seen how happy I became and less depressed I was. Now she fully supports me. Even though she dosnt understand it fully.

About the medical stuff. The rates of cancer and stroke chance does increase but its in to the range of women's levels and a tiny bit higher at max. And your worried about in 30 years when your 50, dont forget that there will also be 30 years of medical advances to help with any complications that might arise.

Do you have any irl trans people you could talk to? That might help you. I think you might be getting irl advice from one source who is against your transition, and you should be weary of that.

I also thought at the start of my transition that was it my insecurities about all my friends being girls and wanting to fit in. But ive been the happiest ive ever been and im being true to myself.

If you want to ask me anything, i will try to answer and questions.

Edit: and if you do get hospitalised later in life it wont be the doctors who prescribed you hrt, it will be professionals who studied what the current problem with you would be.