Fortunately for my family mom lost all interest in driving many years ago (she is now 90 and almost blind... however if you asked her she would tell you she is okay to drive
)
Dad (now RIP) was not so cooperative... long story short is the laws in NJ are like CA. you are forked... we talked to dad's doctors and as you know they can't/won't help. The DMV is... well... the DMV... about as helpful as a baboon on a sinking ship.
We though of sabotaging dad's car... but he would just pick up a phone and have someone come out and fix it (dad was an unstoppable force... only cancer could stop him in the end).
Sorry but we went through years of this... dad was an aggressive driver when he was healthy... he was a terrifying driver toward the end.
Sorry, wish I could help but don't know what to say... I posted the problem here and just got lectured about "he is a hazard to other people you MUST get him off the road!!!" but never found a real explanation on how to get that accomplished.