1. Grease the lockring threads. Maybe a thin smear on steel freehub bodies but I don't bother on alu.

2. When the ribs on the underside of the lockring engage, you'd be able to feel/hear clicks, I normally count about 4 or 5 which is snug but not super tight.

3. I just use a 10" adjustable wrench on the spline tool. Never needed a vice.

4. Yes. I prefer SRAM cassettes on my mountain bikes - shifts just fine with Shimano rapidfire and seems lighter and longer lasting. BTW also recommend SRAM/SACHS chain.