I would be very careful about trying to affect the seller's future sale. If you communicate the survey then fine but what if:
a) seller cannot sell because of untrue comments about his property. (The facts of the survey are one thing, "possible damp" but the assertion that they are indicative of further damage is speculation)
b) seller has to drop price because a surveyor who was working for you has indicated that the price needs dropping.
c) future buyers have to spend money on unnecessary surveys which maybe their own first survey would not have recommended. (Possible damp is a frequent "cover yourself" term for surveyors in houses of that age.
It is nothing more than revenge and makes the whole process very unpleasant.
Essentially the vendor pulled out. You offered below asking, you had a survey done, you quizzed him over damp/floors, you asked for another survey and I am sure gave the impression that you suspected "significant" damp - and therefore the sale was at risk anyway - certainly at that price.
If I were a vendor I'd do the same. You were absolutely right to request another survey if you wanted to be sure. And he was absolutely right if he wanted to pull out and go for a quicker, more straightforward sale.
Think if your "lost" buyers now tell all the local EAs that you are dodgy sellers who pull out at no notice because....., (and they may cite any reason they like), and that is passed on to other prospective buyers.... And you say "No that's not true..." But hey - damage done.
A new buyer will do their own checks and make their own agreement.
It is one thing being fair - quite another to try and screw over other people.