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.
My number one piece of advice is that the best martial art is the one you will practice consistently, more or less. Some have better proven track records than others, but almost all of them will give you a firm advantage over the untrained as long as you practice diligently and efficiently.
Unfortunately a lot of martial arts gyms or dojos are chuddy as fuck, so you may have to bounce around a little to find both a style that you actually like, and a group of people who you can at least tolerate and more importantly trust with your body.
With that in mind, these days people seem to regard some combination of Judo+BJJ+Any striking art to be a good combo, as that would cover your bases in terms of unarmed combat - stand-up grappling, ground grappling, and striking. Wouldn't reach you how to deal with weapons, but weapon arts are quite niche and the rest is more important self defense wise.
If you don't wanna invest that much time, which is fair, out of the 3 my uneducated take would probably be Judo - less likely to be chuddy than BJJ and the ability to get people on the ground while remaining upright is theoretically the best thing you can do in a self defense scenario, as it gives you an opening to run.
In terms of injury, 90% of that is gym/dojo culture. If they don't take safety seriously, have a no pain no gain mindset, use too much force in sparring? You're gonna get hurt. The other 10% is how often you're getting struck on the head. Not doing a striking art, this can be mostly avoided by getting really good at falling properly.