Help making first SQ booking (a few questions)

[alexy23]

New to SQ and the waitlist idea and I've done some researching here so I think I've got most of it figured out.

I'm looking for SYD-SIN-USM (2nd Oct 16). Then USM-SIN-SYD (9th Oct 16).

I'm wanting to fly first class SYD-SIN and business SIN-USM, with a stopover in SIN.

SYD-SIN has the 777 open on F class, but the A380 is on wait list, J class is all waitlist on saver fares, but premium economy is open on the A380 (45k points).

1st Question: Would it be a good idea to book F class (75k points) on 777 as a backup (worst case scenario) and waitlist the A380's?

2nd Question: Given I really want to fly on the A380, should I also waitlist J class on both A380's?

3rd Question: Is there any harm in going "waitlist crazy" and locking into all the different options (every class, every flight) to see which one opens up?

4th Question: Do I need a formal "stopover" to leave the airport (as you can't do stopover on saver fares). Couldn't I just book the flights separately anyway? I worked out the taxes it's about the same.

Thanks everyone appreciate the help!