But idk if it’s really a twin flame connection sometimes because of how fucking stressful it is.

Twin flame relationships can sport most if not all dynamics of common relationships. Indeed some would say tf are on average more stressful.

I'm not even sure there's any feature that is unique to twin flames compared with other relationships save obviously the crazy supernatural events that seem to aid the twins understand something huge is afoot.

Is all this stress and these negative feelings coming from inside me or is it a toxic relationship at the core and I should stay away?

Some may tell you everything is coming from inside you. But without going down that rabbit hole the scattering of problems showing the hardships of proximity with a twin are still signs.

Similar to synchronicities showing you the road you are walking or might wanna walk, problems are showing you the road you are walking and might not wanna walk. It's up to you according to your specific situation to choose whether to deal and solve issues or forsake that road altogether possibly temporarily.

I would expect packed with signs showing problems would also come signs showing solutions. You are totally right in not wanting to deal with what you call toxicity but it takes two to push each other's buttons.

I just don’t see how this can be healthy

Because it's not. It's like being sick, it's not healthy, it's a condition that warrants taking steps and time to heal. In another post you wrote:

What do I do to maintain my trust and faith in this process?

I would focus less on the problems, only as hints to find my way out in the same way feeling pain on my fingers makes me take my hand off the stove. I would listen and heed signs showing me the way. I would be thankful for any sign showing me the way.