So, I want to do some martial arts, for self defense. Ideally one that will be useful without giving me CTE, or any long term bad stuff, even though I feel this is already asking for too much 
I don't live in the U๐๐ so gun related stuff isn't really an option.
I'm somewhat heavy, with a year of experience in lifting, and my cardio is not the best, but I can do long walks (of 1 or 2 hours) before getting tired.
I'm going to move to a bigger city in September, and there's a lot of stuff available, so you can comment on the more niche options.
So yeah, any advice from your experiences is welcome lol
If I had known people started arguing over my post I wouldn't have made it.
Here's my two cents because I agree with your sentiment but would like to suggest different implementation.
With a collapsible baton you still have to be physically fighting someone. It is a pretty nasty weapon and you could catch charges for being too quick to use it. They are illegal in many jurisdictions. Sure you could hurt someone with it, but its not disabling and a determined attacker would persevere. So what purpose is actually served?
A stun gun again relies on up close contact and again being ready to mix it up in hand to hand, suffers varying degree of loss in efficacy through layers of clothes, and (this part I am uncertain on) does not disable through electric shock but again merely relies on pain.
Pepper spray requires no particular strength or skill to use, and will temporarily disable an attacker by forcing their eyes closed with tears and disrupting their breathing through coughing spitting drooling snot.