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.
Maybe consider who you're talking to and what kind of perspective they may be coming from. If someone is putting their hands on me, there's probably a 98% chance they're bigger and heavier than me.
As said in another comment, I am a trans woman, I am in precisely the same situation.
That doesn't mean what your were suggesting isn't bad advice to give to others - again, if someone put their hands on you then your firearm is going to be extremely difficult to use effectively. Martial arts are genuinely the more suited tool for the situation, strength/size can be overcome - at least momentarily - with technique even when the gap is large, and all you need is to create enough space to either run, draw your weapon, or both.
It's definitely a lot harder for women, but it still very much can be done and knowing how to do it only makes a firearm more effective by increasing the odds that you will actually be able to use it.
Which is why you train to use your firearm quickly and from inconvenient positions.
Frankly, I just don't agree with the notion that guns are useless within 21 feet. That's cop pseudoscience.
Just because cops are saying it doesn't mean it's not true. There's actual studies on the matter and they've done testing. Drawing a firearm and shooting accurately enough times to consistently disable a human immediately - so at least two shots with handgun calibers - is extremely difficult and cannot be done consistently within that range or closer, and again most self defense starts within or just outside arms reach.
That's a large part of why they themselves teach police basic grappling. Most of them aren't any good at it, but they are still taught it for good reason.
Again, it's a matter of consistency - if you try to draw a firearm when someone has hands on you, they are GOING to attempt to stop or disarm you by grappling you, even if likely in a clumsy untrained way.
Obviously, it's much easier to resist grappling when you yourself know how to grapple. It's a skill, after all.
21 feet might be ideal conditions but if their hands are on you already how the fuck are you getting a gun out and pointing it without surrendering the grapple?
do you have three arms?