$temple.xp_gain() and $guild.xp_gain() also use the same system if I remember correctly.
I believe inventory.append([item, amount]) is how you can add items but not all item names make sense.
Also you can change the adjustment amounts (exercise increasing multipliers) with:
player.intmod
player.adjmod
player.endmod
player.strmod
There is a direct method to set title levels but I do not recall that off hand.
Your total affection for titles is calculated on revival for so you need to up the Lani or Marla affection to see that title be quickly gained on rebirth. I believe lani_affection is the variable for Lani but am not 100% sure.
A thing to note is that once you unlock a level of a title it's benefits are passed as they currently exist into each rebirth via an array so even if you change their values in the files you would need to do so on a new save or possibly reset your titles levels to force it to recalculate. The only title based value that this might not apply to is the statmod titles as I believe those are recalculated each revive individually.
You can add in any other value used to calculate for titles they normally start with $ and then some form of description of the variable but I do not remember each off hand. They likely can be found in the rebirth_summary rpa file.
