I can't comment too much on whether your car is a SE or not, but perhaps a look at
http://www.socal240sx.org/faq/1991.html could help you out.
The timing chain noise on the DOHC engines is often caused by the upper guide, which is often removed to remedy the problem. Take the valve cover off, and I believe two bolts hold it in, and see if that gets rid of it. Tensioners are also a strange thing on our cars . . . I have a SOHC model, but the original engine in the car had a timing chain wear a hole through the front cover before I got the car (which killed the engine eventually, but that's another story), and after installing a new engine, the new engine's tensioner was not working correctly after a month or so of being in the car. Go figure . . .
I would check your rear brake pads/rotors for that grinding noise, also possibly a frozen parking brake. I had the same problem on mine, it was just worn pads. Hope that helps you out . . .