They need water just as do rhodies do.

It's in an area that is too dry for it now that it has grown larger. Move it to a more suitable place. Right now it's under the eves and too close to the house.

Looks terrible - that is your sign of disease. Since it is dying away in sections it might be something like phytophthora root rot - root samples may need to be taken to the King County Cooperative Extension office, sent to a lab for testing to find out what specific issue is present.

Otherwise, yes these like to be kept moist in summer. Part of the species' natural distribution includes Yaku Jima island, where the annual rainfall is in the hundreds of inches.