Village Idiot,
I think you, with the help of others, have convinced yourself not to take on the work.
What the....is wrong with you and others!
Has there been a positive post about this thread...no...all negative.
From what i can gather, you don't have any confidence in yourself or your ability to undertake the tasks requested, then you advertise the fact in a public forum.
How about being positive, go see the bloke and nut out a deal that suits you both.
I don't see the situation very different from quoting a customer for a boiler changeover.
You are most probably quoting against other contractors, offering the same services at around the same price. Who wins - the Plumber whom the customer feels most comfortable with.
This situation is no different - just on a larger scale.
You thinks this bloke has got you by the balls, by what definition.
You haven't even sorted out a price yet - nor a contract.
If you agree to a deal, that you believe you have been had, then you are only to blame.