it doesn’t sound like he’s inclined to take your advice anyway so why worry? you already did your best to try and nip this in the bud, the consequences aren’t yours to deal with…
he should have taken your advice to begin with. not buying, not signing is so simple and easy and obvious. trying to extract the deposit is not so simple and easy and obvious. you gave him good advice that would have avoided the whole situation, you cannot now give advice on a complicated matter that will fix things.
i think i’m trying to say that you have no experience, no blogs, no knowledge to draw from to give any credible advice at this point. and to not put yourself into a position of giving failed advice, of having the responsibility for failure.