(I'm assuming you are in the United States, some states have laws that make it easier to convict pedo's, but this applies to anywhere in the US)
From what I understand, the best chances you have to get him in trouble, You have to set up a meet up with what he believes is a underage minor. That is the only way that those messages can be used against him, some law enforcement agencies will act just with the messages and evidence you've collected, but most will just chastise you for doing so, but if you get him to attempt a meetup, and he is found in or near the location designated for the meet-up of what he believes is a minor, then MOST law enforcement agencies will at least charge him with what is call "Luring a minor." Outside of that, it depends on the agency you deal with, from what I've seen, most won't do anything UNLESS you do the whole meet-up deal, even then some won't do anything, but the chances of him getting charged go WAY UP with the meet-up.
Like I said though, it depends on the law enforcement whose jurisdiction it would fall under, good thing is you have his picture, but most cops will say that they can't PROVE it was him, he could just say it wasn't him using the device at the time, and they used his photo, but if you catch him at a meet-up location with the conversation, including talking about the meet-up, and the conversation must show that he was there to meet 'what he believes' is a minor, then chances of him getting in trouble go WAYYYYYY UP.
Keep it up, we need more people out here protecting the kids!
I would maybe report it to the police to see how they act, and how they say they will handle it, then if they respond the way I've seen many, they won't do anything, then you can try the meet-up, but the meet-ups give you the best chance to put him behind bars, because then they at least have evidence of Luring.... and I kinda understand the cops, because if they bring charges on someone, and the attorney cant prove them in court, the cop gets in trouble. It's hard to argue with catching them at a specific location at a specific time, expecting a minor to show up...
Even just getting him to agree to meeting up somewhere, makes your chances go up, but meeting him on location is like the nail in his coffin.
If you do go with the meet-up plan, Inform law enforcement before hand, they may try to discourage you, but there is nothing wrong with what you are doing at all, that guy is the problem.
DO NOT GO MEET THIS PERSON ALONE, have others go with you, If they are willing to harm a child, they will probably be willing to hurt you in an attempt to save themselves, and you should ABSOLUTELY RECORD EVERYTHING starting before you ever get near the location... Also, if you think he wouldn't meet up because of the distance between you two, give it a shot anyways, I've seen many many videos where one of these pedo's drive 4 or 5 hours, one I seen he drove for over a day.... But catching him talking about meeting up with a minor in the discussed location is your best bet.
Also, if you do go through with this, please post the recording online, if the Judicial system won't get them, the court of public opinion will.
The only other thing I can think of that will be nearly as effective would be to get someone to be an actor, pose as a minor, and record a video call between them, raw footage, and discuss things on the video call that would be damning for him, but the meet-up is hands down the most effective way to put this pedo in jail. If you do the video chat thing, make sure to discuss meeting up, and give him no reason to believe you are not a minor, at the very least it will be an addition charge against them.
PLEASE KEEP US UPDATED, I would like to know how this goes!