3/4mm above the full mark shouldn't cause any harm.
Yes, any brand filter designed for the 1996 Camry/Vienta V6 will suit the Soarer.
Not sure about Magnatec. I've been using Mobil 1 since I bought the car, and haven't had any problems. Peter Scott from PlanetSoarer knows his stuff, so I would trust what he's written on the site.
Yup, 18"x8" wheels on my car. My Soarer is lowered a few inches, and my 18's fit on without any modification whatsoever. The Soarer is very accomodating for large wheels. I just put them on and have never had a problem with them.