passfan: these are all legitimate questions that need to be addressed to a competent halachic authority familiar with this specific area of halacha. Might i suggest not simply asking ones LOR. These are detailed choshen mishpat shaylos and need to be treated as such.
I think we all agree this is not the forum (and I am most definately NOT qualified) to answer such detailed questions.
All I would like to accomplish is to educate that your very valid questions are no different when relating to shadcnim as they would be to a private math tutor, a plumber, electrician or any service provider or broker who does a job without having a pre-arranged agreed upon fee.
These things happen every day (like a babysitter for example), and they need to presented to a qualified authority who is familiar in this area of halacha.