My partner and I currently live in Australia and we are planning to move to England mid-next year. We have a registered relationship in Australia.
He has Australian and Irish citizenship so we assume he would be covered by the CTA (Common Travel Area) agreement and would have no issue settling.
I only have Brazilian citizenship and as far I know I would have to apply for a family visa through him if I want to live in England.
I've got a few questions and would love if I could get some help!

1 - Am I able to apply for a family visa through him while we are still living in Australia? Or can this only be done when he starts living in the UK?
2 - If this visa can only be applied when he moves to the UK, is it a better option to get a visit visa and switch visas over there?
3 - Regarding fees, do I have to pay for the family visa fee (£1,523) + Healthcare Surcharge? Is there any other fee I'm missing out?
I’d appreciate any and all help!
Thanks!