For the sake of correctness...Cupressus nootkatensis.

Your looks to be the cultivar 'Pendula'.

I know at this stage of the game you could care less.

Every so often these conifers will defoliate to some degree but not to the degree you say yours is.

The salt water and the time of two weeks addressing the issue will eventually cause its demise..In fact there isn't anything you could have done to save it in my opinion.

The fact it is defoliating at the top is a concern. What you loose will never regenerate. The greening up at the bottom is worth nothing if everything is gone at the top.

I would say it its toast.

Others may have a different opinion.

Dave

what he said ....

but more importantly.. its what i believe is your front door... this thing has to irritate you every time you walk by it.. and perhaps in your sleep.. get rid of it ...

time for something new...

ken

Gypsum would be of little benefit in your scenario.
Even less so now, the Nootka Cypress is already past the point of no return.
See article below...

Here is a link that might be useful: Salt Water Inundation from Hurricane Sandy