Thanks, I appreciate the help!
Next application question... Under the employment section it asks for my total monthly income. I am a non-exempt employee paid hourly so my monthly income varies. Should I give an average amount?
Yeah, just give an average - it's not relevant to the application anyway.
They also ask if I've ever worked for the Government (Central or Local) . I worked for the IRS for several years which is federal. Is that what they mean by central?
I assume so. Just doing a Wiki search, it sounds like there is a 'central government' in sovereign states (like the UK) and the equivalent is a federal government in federal states (like the US). So if you worked for the IRS, that would be considered 'central government'.
Lastly, do I need to provide any employment documentation of my own? I think I read in another thread that it's not necessary.
No, you don't, because it cannot be considered for the application.
The online application form is fairly generic and not all questions will actually be relevant to every visa type. For a fiance/spousal visa, the applicant's income cannot be considered, so is not relevant. You still answer the questions, but your income will have no bearing on the application.
However, if you were applying for a visitor visa, your income would be important, because you would need to show that you had a job to return to in the US to prove you would not attempt to overstay your visitor visa.