Partner Visa

Hi there,

I live in Thailand with my partner and have a couple of questions which I'd really appreciate some assistance with... I am a UK citizen, my partner is an Australian citizen and we have been in a de facto relationship since meeting here in Thailand approx 18 months ago.

Q1) My partner works as a teacher here and paid in Thai Baht so his salary on paper looks very small (AU$11,000 per year) and he has no savings or property in Australia. How will this affect the assessment of his ability to meet the sponsor's responsibilities (I have an income from property in the UK and some savings, does this help or it's possible his parents would act as guarantor if this would be of benefit?)
Q2) What are the approx. timescales for grant of temporary (2 year) visa (it says approx 5 months on the immi website) and once granted, what is the usual timescale for date of first entry. Also, is it possible to validate visa by "holidaying" in Australia before making a permanent move?
Q3) On form SP40, there is a question for my partner about whether there are any "outstanding debts to the Australian Government or any public authority in Australia?" My partner apparently has numerous unpaid parking fines to the state authority which may have proceeded through to court / collection but we're not sure. Any advices?
Q4) Is it worth engaging an immigration agent. Does this provide any benefit, i.e. are they able to negotiate on your behalf.

Apologies for the mass of questions. Thanks in advance for your help!