Sounds like your realtor is the listing agent as well as your buyer;'s agent.
(since you said he did the open house)
The agent can not give you details of the other offer, such as the amount they offered or the terms. He can say if it was a full price offer or not, but not more than that.
It would have been nice if you at least got a counter, then maybe you could have increased your offer, and take away the request for closing help. It is up to the seller to decide which offer they want, as well as which ones to counter.
In a seller's market like the one we are in now, sellers are not likely to pay any closing cost. Offers asking for closing cost help will not be favored in most cases.
In my opinion, your seller did nothing wrong.
Try and stay positive, and keep in mind it will take several offers before you get one accepted.
Best of luck to you!
Kawain Payne, Realtor