1) When you use a curse like an artifact, it follows all other artifact rules. So, you can't have a curse and another artifact active in your artitfact pile at the same time and just like artifacts, mass effects affects everyone (e.g. Plauged With Desease (though, since that says "your opponent", you are not affected by it)).
Also, PWD's effect lasts until the curse is deactivaed (or negated).