Hi Leseven, and welcome to the board.
I usually stay at the Nana hotel in Bangkok, but would not really reccommend it for couples. You will get lots of choice in that price reange tho, and I'm sure other BMs will point you right.
Patong, I would think somewhere like the Expat, E-mail:
expat@loxinfo.co.th would fit the bill, though there will be others.
As far as food goes, you are visiting a gastronomic paradise, all the street stalls and noodle shops in Thailand will feed you for pennies. The food culture in Thailand is fantastic, and cheaper than Melbourne, enjoy.