Hello, I can not answer some of your questions but I know having some info is better than not having any info.
To legally work and get paid, your husband must also have a work permit. Typically the expat spouses come in on a dependent visa which does not allow them to work. Also the work visa must be associated with the employer. So you can not get a work visa from the farm and work elsewhere. Make sure your employer does not expect (or try to leverage) a 'twofer" meaning he pays you and expects the husband to work also. It is not really easy to change visa and sometimes you have to leave the country so explore this up front and get the company to pay for the work visa if interested.
Cost of living in POM is high.  Typically an expat will get a package that includes: salary, housing, utilities, phone, car and fuel or at least use of a car and driver. Usually your only expenses would be food, household and personal items. My wife and I can spend USD up $1000 a month,which includes food, occasional new clothes, eating out or going to a movie, internet (which can be expensive) and other discretionary spending.
There are a number of private International schools here. Since I do not have children with me I suggest you start another topic and ask specifically about schools and education.'
I pray everything works out the best for you. please fee free to stay in touch or Private message me.
( I work for City Mission PNG, A Christian Non-profit, NGO in POM.)