Yeah, we're on the same page for Parson possibly being what the Erfworlders considered a Titan, and for him being supernatural. After all, the Stupid Meal listed him as being 'Chief Warlord, Level 2, SPECIAL.' In my experience, anything involving a tabletop game noted as special is usually some kind of ability that doesn't fit into the ruleset. But, once again I must stress that if he is a Titan Parson was not the ONLY creator of Erfworld, he only created some small portion of it. After all, think about just how many gamers are out in the world today. Hundreds of thousands, if not upwards of millions. Thus why he would recognize sections of it, such as the battle he was in, the concept of stacking bonuses, and how he recognized the potential exploits within the rules system, but how he was utterly unfamiliar with other concepts, such as royalty, movement, turns. A lot of that can be attributed to being just out of place; after all, how would you feel if you were stuck in a wargame like Warhammer 40k? "Damnit, they are charging right towards us! Lets just shoot them!" "No, its not our turn, and we aren't in cover."
For number 2, Parson having the power of Titans without realizing it, well, that wasn't exactly what I was trying to say. Really, the point of debate is what exactly a Titan CAN do, and that revolves solely around the crux of the issue; if the Titans created Erfworld, were the minds of gamers such as Parson these fabled Titans. It is possible that, assuming that there are an infinite amount of universes like you hypothesized, that this is a cosmic coincidence that the Summon Perfect Warlord spell, which recieved a hot beef injection of Fate magic, drew Parson to Erfworld as the best match for a Perfect Warlord. What I think I'm trying to say is, if gamers created Erfworld, then while they have power outside of the world in its shaping, I believe that while they are in the world, which is partly supernatural and mostly just an extremely unnatural and chaotic situation, what advantage a gamer/titan draws is the same as any advantage that they have when they are playing against an AI opponent or someone who is stuck inside the box.
As an example, imagine if you will playing Alpha Centauri. The computer players are predisposed to strive towards certain objectives, whether they be a Transcendent victory, a military victory, diplomatic victory, what have you. As a human player, though, you are able to think beyond 'what is the goal', to 'how can I best achieve the goal.' Human players can act upon plans that, while they function within the existing ruleset, are not what the ruleset is intended for, which is often referred to in games as exploits or bending the rules. For example, one game of Alpha Centauri, the campaign was drawing to a close, I was nearing my goal of a Transcendant Victory, but I knew that Chairman Yang of the Hive was nearing a diplomatic victory. He was in too powerful of a position for me to eliminate, the diplomatic victory would trigger before i transcended, and the Greenpeace hippies and the Spartans hates me. My only ally was the University, who I had kept alive to trade techs with to speed my way to transcending. I couldn't for the life of me figure out a solution until I realized that the Spartans, having been relegated to an island for the early part of the campaign, had been at war with the Greenpeace wannabies for the past 20 turns, but didn't have the technology or manpower to defeat them. So, I did something the computer wouldn't have been able to trick a human player to do. I immediatly gifted all of the techs I could to the Spartans as well as my healthy surplus of resources, among the techs all kinds of psi defense to counter the mindworms the Greenies were using. The Spartans were wiped out by the combined forces of the Greenies and Hivers coming to the Greenies rescue, after the Greenies had been reduced to one colony. Then, I convinced the University to attack the Greenies, which after the Hivers interceded one turn too late, resulted in the Greenies and the University being wiped out, leaving just myself and the Hive, rendering a diplomatic victory impossible. In the meantime, I had secured peace agreements from the Greenies and the Hivers immediatly after war was declared, allowing me to focus my resources solely on technology. Overall, these individual plans and the overall strategy were just beyond the AI's ability to comprehend, and even when it was too late to stop me I don't believe the AI realized what happened, as the Hivers kept trying to bribe me into voting for them in UN elections.
So, TL;DR: Parson's 'Titan' abilities within the physical realm of Erfworld are not of the omniscient 'I can make an unmovable boulder for shits and giggles' kind, but of raw human intellect that is beyond the capabilities of native Erfworlders. Throughout the series, Parson has asked questions that no Erfworlder ever actually considers. The epic speech concerning the difference between a strategy and a plan also is treated like a kind of enlightenment by the Erfworlders, whose entire existence revolved around waiting for their turn to start and marching gloriously into meatgrinders. Just like the titangamer theory states that the minds of gamers created Erfworld, it is the minds of gamers that give them such unparalleled capabilities while they are in Erfworld without being actual gods. After all, the fact that Gobwin Knob still stands and the entire Royal Crown Coalition army was annihilated is a miracle, but it was not a miracle born of divine smiting, it was born through sheer intellect and determination on the part of Parson. And once again I repeat, the reason noone considers Parson a Titan, is because those on Erfworld believe Titans to be these colossal omnipotent, all powerful beings. Not a warlord whose intellectual capacity is so far beyond theirs, most of them don't even realize what Parson is capable of.
In fact, the one hole in the entire theory, as I see it, is the existence of Charlie. Charlie is the one resident of Erfworld who even comes close to understanding what occurs in Parsons mind, and the only resident of Erfworld who partakes in the same mindgames as Parson. I was tempted to say that perhaps Charlie is of the same ilk as Parson, a gamer drawn into Erfworld by magic of some kind, but then, he is attuned to the Arkendish. The Arkentools I can see, within the scope of the titangamer theory, as one gamers insertion of superweapons into the game. But so far, they have attuned to Stanley the common infantry unit, Wanda the caster, and Charlie the X. Charlie, who is unique in Erfworld in that the only person who thinks like him is Parson, who doesn't come from Erfworld. The only way I will be able to throw my money one way or the other is to see if the 4th known Arkentool, if it hasn't already attuned to someone, attunes to Parson. If an Arkentool attunes to Parson, who isn't from Erfworld, then I would say that Charlie is also a titan/gamer, trapped in Erfworld, attuned to the Arkendish, and manipulating everyone against each other as a mercenary doombringer with his army of archons he gained from somewhere.