Passenger CV joint and one sided rear brake - 2013 Plug-in, 230,000 miles

IMHO: I would take it to a tire & brake repair shop. There's nothing special about the suspension & brakes on this car that requires dealer intervention. I would do the work myself. 1.0 to 1.5 hrs per half-shaft (~$75 each rebuilt or $300 each new OEM) and 2 - 3 hours on the rear brakes; depending on the amount of rust on those calibers.
The reason the shop is incentivizing you to replace both half-shafts and not offering a boot replacement is based on the mileage of your car. If I owned the shop, we would both be peeved if the other side failed a few weeks or months after replacement. Bad feelings all the way around, from a warranty work perspective. That's why most respectable shops won't do "patch-work" - it's all or nothing.
The rear brakes calibers needs to be rebuilt or replaced, because the slide pins the calibers float on - seems to be frozen in place. Just regular braking should've scrubbed the rust off those rotors, just like your front. You shouldn't have to resort to B-mode to clear rust off the rotors, unless something isn't working correctly. New calipers ~$90 or rebuilt ~$60 each - pad and rotor kit ~$70 pair.

Hope this helps....

PS: make sure the shop disconnects the battery, BEFORE cracking open the brake lines. If they don't know this - DO NOT get the work done there. Flush-out the entire brake system with new brake fluid while your there.