Yes - cut them back to the SIXTH node from each trunk - it will go dormant for a while and re-flush.

Not necessarily :-)

Wisteria is sometimes prone to a very sudden and rather rapid dieback, which is usually fatal. Just Google 'sudden wisteria death' and see the number of hits that turn up. Usually it some sort of root rot, like phytophthora or honey fungus (Armillaria spp.). But similar symptoms can be the result of significant drought as well.

I would certainly cut it back hard but no guarantees on how well it will respond.

well.I went to cut back the wisteria today and when I got near the bottom, the main plant just pulled out of the ground. The stem was all soft and rotten... Hope my other one does not do that.

Thanks