A few basic questions… for some

Can someone please confirm my thought process on this matter.

I am finding it quite challenging to get a straight answer out of certain brokers/banks etc. Everyone seems to say something slightly different which is of a little concern.

I am looking at NAB choice package which currently have a 95% LVR.

Lets say for example my proposed loan was for 550k. LMI and other fees  such as stamp duty charges equal 30k.

Can i add LMI/stamp duty etc to the proposed loan, now making it 580k? or not? 
 
My understanding is i now need 5% on 580 not 550. This is a minimal expense on a monthly expenditure, but wondering if it can be done, or whther the banks like you to pay the LMI  etc independately.

From my maths the total out of pocket expense is only 29k V's 27.5K on a 5% deposit, which is significantly lower than the 27.5K (5% of 550) + 30k in LMI, fees etc, which is the scenario i would like to avoid.

Can i also ask if you can apply for offset accounts for interest only loans or do you need P&I to take advantage of this?

Another silly question, based on an interest only loan, my mortgage repayments should decrease from month to month if i am utilizing my offset acount effectively?

I know that some of these questions are quite basic but i would just like some confirmation around them as i cant seem to get consistant answers.  

Cheers,
Steve.