Also did the other buyer pay "ALL CASH"? Was your offer also ALL CASH?
If you are going FHA with only 3.5% down it may be more risky for a seller to accept an offer from you because the house needs to be in fairly good condition to pass the FHA appraiser's inspection. For example the roof must have at least 2 years of life on it, no peeling paint, no rotted wood on eaves, no exposed electrical wiring.
The only case you may have against this realtor is if he DID NOT present your offer to the Seller. If the Seller chose to go with a different buyer well there is nothing you can do about that. Also have you considered the listing agent was offer "additional" commission by the buyer that ultimately got the house? I have seen this happen when there is a spectacular bargain priced house.
That's another problem, if this was a "regular" sale (not a short sale or bank owned) then it appears the Seller may have sold too low based on the fact that multiple buyers were clammoring for the property. He may have done his seller a serious injustice! You may even want to try to contact the previous owner to see if he was ever presented with your offer. If he wasn't that seller may be furious and take legal action against the listing broker. Then you may have a case against this Realtor! You wouldn't be able to reverse the sale but you may be able to inflict some pain on him with the formal complaint process.
Hope this helps and immediately go find a Realtor you and your husband are comfortable with. As you can see you had no advantage by going through the listing agent directly!
www.DaveRamsey.com has Endorsed Local Providers in Real Estate so you may try there for an agent.
Good luck on your nome search!
All my best,