[RIP]

It's pretty obvious your current mechanics are missing something and you are paying the price. It's far past the time to take it somewhere else. Do some research and ask around for the best place to go.

Don't see any recalls or service bulletins effecting your problems. There's complaints about brake noises but, that's about it.

Bleeding the brakes after ABS system component replacement on these vans requires the use of a scanner tool and can't be bled in the normal way. Are they doing that? If they are repeatedly bleeding your brakes you either have a leak somewhere, the seals in the master cylinder are bad, they are doing it wrong or as you say they are tired of seeing you and want you out of there pronto. That brings us back to my first paragraph.

Another cause of spongy brakes is a weak booster. Let it run a minute or so then turn it off. Now apply the brakes. Should be firm pressure for at least two to three applications. If not, the booster or it's vacuum source is bad.