Aescarnite

For some reason I've become slightly obsessed with FF programmes/rewards etc and was delighted to find this site full of apparently like minded people! However I'm still finding my feet and haven't quite made the plunge yet so I am looking for a little guidance...

My situation

1. Currently living in the UK, currently an infrequent flyer.
2. Moving to Darwin, Australia in Feb 2018 and looking to become a slightly more frequent flyer.
3. Currently have no status/miles on any airline FFP, however did join Qantas FFP a couple of weeks ago (and managed to avoid the joining fee as not yet and Australian resident!)
4. My partner and I will be travelling back to the UK 1-2 times/year (ideally to MAN but LHR isn't too much of a hassle either)
5. We will make a few Australian domestic trips a year (say total of 5 each?) to TSV, BNE, SYD, MEL etc in economy
6. We may have one trip each to SE Asia each year in economy.

Goals

Primary - The odd return Biz flight to UK for partner and I, or if this is totally impracticable, the odd return Biz to SE Asia.
Secondary - Access to decent lounges both domestically in Aus and on international flights when flying economy.


Questions

1. Do any of the Australian credit (or charge) cards offer a "companion ticket" option like the BA Amex card in the UK? From the research I've done so far it doesn't look like they do...
2. Qantas FF seems pretty hard to earn (decent) status on, compared to say, BA (tier points seem to be easier to earn and the thresholds for oneworld lounge access are lower) - is this your experience?
3. One the above point - I'm half thinking of doing a couple of mileage runs/holidays before leaving for Aus to try and get BA Gold status (oneworld Emerald), but then wonder whether in the long run that's the best thing given the fact I'll be wanting to fly domestically around Australia - what do you think?
4. Given the amount of flying I'll be doing I don't expect to earn too many miles/points from that, and expect most of it will come from credit/charge card spending. However, converting Amex MR etc to Qantas points doesn't seem like the best deal cf Asia miles and so I was planning on putting all my points from spending into something like Asia miles and leaving the flying miles as Qantas points - does this seem sensible, or am I running the risk of not being able to achieve my goals (above) since I've spread it across two programmes?
5. Credit/charge card bonuses - there seems to be some pretty good deals on at the moment (e.g. AMEX Explorer with 120K points and a $400 travel credit) but will expire before I arrive - do these seem to be repeated fairly frequently or are you currently experiencing the best deals?
6. Are there other obvious things I need to consider that I've missed out here?

Really appreciate any help from some of you more seasoned travellers, I've really enjoyed exploring and lurking in the forums so far and promise to contribute more when I have more to give Thanks in advance!