I don't know the Intex SWCG, and I'm not the SWCG expert, but I'll bet you've been running your unit 'WAY too high! With a CYA of 70, your FC target is 3.5ppm or more, not the 5ppm -10ppm range in the Best Guess table.
Generally, you do NOT want to depend on your SWCG solely for chlorine generation for just that reason: You shorten the salt cell's life. So you should be adding bleach or liquid chlorine when you need additional, and run the SWCG to keep the maintenance level, and no more.

I don't like to say bad things about Intex, and I won't because I happen to think they make a GREAT product for what it is: Inexpensive starter pools and equipment, even though filters tend to be inadequate. My first pool was an Intex donut and it gave us 3 great years and didn't owe us a dime. BUT...their mechanical equipment isn't robust, isn't designed for being pushed to its limits and is always a bit suspect. I suspect you've pushed your SWCG far beyond its capability.