Long story short we are 5 months into a deal and my seller has chosen to rely on non-M&A experienced friends and his financial adviser to tell him if my offer is good enough. Let's skip ALL the reasons why that's an awful idea and go straight to the pros/cons of me recommending (and maybe even paying for) a broker or experienced sell-side adviser to guide him to the finish line with sound and experienced M&A advice.

My biggest fear is that the broker or adviser I recommend he use comes in and either:
a) introduces more buyer competition
b) puts the deal on the open market
c) advises the seller to work on the business for x number of years before selling.

...ALL of which could kill my deal.

How can I be assured that the broker/adviser will come in and work toward OUR deal? Anybody else run into a seller like this? what did you do to overcome? Thanks for any help/advice you can provide.