That said, again, dishwasher detergent is basic, so you’re right in that adding acid probably won’t improve the efficacy of the wash cycle.

Though I can't confirm this, I suspect that the vinegar is mostly removed with the the pre-rinse water, which may negate or disrupt an added pre-rinse detergent, but should be mostly gone by the main wash to not effect the main load of detergent released at that time.

The spindle that supports the basket in washers is made of unprotected aluminum and designed to fail at about seven years of use. On Bosch models, they seal this in so it cannot be fixed.

https://www.mcmaster.com/product/8986T16

You could try something like that, then you would have to also pick some fittings to match whatever your dishwasher supply line uses. You would also need another short hose between the filter housing and your dishwasher. I think you could recharge the cartridge by soaking it in salt water occasionally, but otherwise they sell replacement cartridges.

I don't fully understand how this works. The pump and valve are used to circulate hot water though the hot pipe and back through the cold pipe.

But... doesn't that mean you never have cold water? Because the cold pipe is by definition also hot now?

It seems as if this just shifts the problem from "wasting hot" to "wasting cold" to get the water you want.