As others hint at you have the option of applying now through the SMC process. Onshore, in New Zealand, you might expect that most branches, including Christchurch would take around 4-9 months for the end to end process, so you might expect to have your residence sometime between June and October. If you wait to till June to apply under the "Residence from Work" rules, then those applications are treated as a priority and would likely take 1-3 months to be approved. So under that process your might have your residence sometime between July and September. (Not much in it really time wise.) The costs are , as you point out more under SMC. The other advantage is under the Residence from Work process there are less requirements and rules than under SMC. In most cases if have a work to residence visa and then start the SMC process immediately you would be better off, but not in yours as you have left it for 18 months.
The difficulty is that if your partner goes to work in Australia, then there will be issues with you not living together, and whether he can then be included in your application. I'd say there, 'short term pain, for long term gain", so wait until you have residence before considering him going to work in Australia.
As far as working towards Permanent resident Visa, the rules only apply to you, assuming its you who is the principle applicant. Your partner can be off shore for as long as they like.
(Right now you well find that the employment situation in Australia is even more difficult than in NZ, they are in the middle of a huge downturn!)