I am not familiar with an apartment complex thats called Castle Peak Bay, unless they meant the Gold Coast residences located on Castle Peak Road.. I'll check on that though.
No matter, the Gold Coast has a number of CX cabin crew, and there's a few pilot families located in the area as well, because of the easy convenient proximity to the airport.
The Gold Coast apartment complex has its own airport bus for residents, and you might also be eligible for an airline industry discount card that's attached to your octopus card, which gives you discounts on all public transport here etc. You also get an airline industry reduced fare on the Gold Coast airport bus , providing you are a resident of the complex, which i assume you are. If you are not, just make friends with a GC resident and just buy the vouchers through them.
Whether you can live comfortably or not, is entirely based on you, are you are frugal person, who saves money usually, or are you the type that spends most of your free time in bars, wasting money on drinks/clubs ?
Considering that your housing is provided, and that you will be out of the country roughly 50% of the month, you should be able to easily save $10,000 per month without trying too hard. Also remember that the average salary in HK is about $10,000 per month, and locals don't typically, if at all, get housing provided by their employer. I'd be amazed if you couldn't live comfortably on $20,000 per month, with a level head.
We also live in the area, and absolutely love it, and its no big deal to jump on a KMB bus into Central, for a night on the town every once and a while, when you feel the need.