What are the symptomps of your illness? (if you're comfortable with sharing). And how do you "reduce ER stress"?

There are a number of ways to reduce ER stress and I'm far from an expert, generally anti-oxidants do the trick, if you have a similar illness I'd look up studies for your specific illness, they often do in-vitro tests of specific compounds to test their effect on diseased cells.

In my case I try to avoid alcohol, and I supplement with high doses of rosemarinic acid extract.

Not in the field but I’ve heard that fasting allows the body to consume mis-formed/old cells. Is that something that would help in your case? That and keeping mtor low perhaps?

You're looking at this from a healthy body's perspective, in case of an excess of misfolded proteins the ER stress increases which activates the unfolded protein response (UPR) which tells the cell to produce less proteins to let it chill out a bit, and then if the ER stress remains too high leads to apoptosis (cell death). That's the way the body normally functions and it's all good.

But if your body produces a majority of misfolded proteins you don't want your cells to freak out about it and kill themselves because you need those cells alive for your body to perform its normal physiological functions. At least it's an emerging theory that in some case the systematic destruction of the cells leads to worse outcomes than just having cells living and working with misfolded proteins.

Take all this with a great big grain on salt because it's the blind leading the blind. I'm not a biologist, I've just read a lot about my illness.