If I have begun working with a commercial broker in a certain area and we have an informal agreement that I am working exclusively with her (we haven't looked at dozens of deals together or anything, but we've talked about two or three), and then I find a FSBO deal in that area and contact the owner directly and start negotiating, should I let the broker know as a courtesy or even a moral obligation?

You have no moral or ethical obligation to disclose any details. 

My experience with the Larry Goins Group contradicts several of the points in their  Mission Statement and Core Values:I take issue with the last line of the Mission Statement that reads:"based on ethical, moral and biblical principles."

Have seller carry back, to boost Cash RoR?

Realtors are sworn to adhere to a moral code and I , personally, feel that this is an ethical lapse.

We then come in as the equity investor to cover out of pocket costs (inspection and appraisal) and holding costs (6 months worth).Used correctly leverage will boost your returns while allowing you to shift risk to the 1st and 2nd mortgages. 

I have 1,000 credit limit, can I also boost my credit by adding 500-1000 of my own money?

Most banks are going to require that you have two years of steady payment history on the job before giving you a loan.There is a service called Experian Boost that can help build your credit history using, cell phone payments, streaming services, and your other bills.If none of the above are available to you, the next strategy may take six months to a year.You can get a secured card through your bank or credit union.

Just think of your mom and dad or your grandparents when you embark on these ventures.. and how you would like them to be dealt with then let your conscience guide your actions.Remember in BP your a hero if you rip 50k out of a wholesale deal even though the seller should have gotten most of that for every wholesaler who takes a HUGE cut above industry norm there is a seller losing out.. so again.. its a morality thing as well.

A new ruling in 2016 allows you to write off a lot of items for big boosts in tax savings.