The underground bit rubs me the wrong way. Most reptiles tend to be endothermic and don't do very well in dark and cold conditions. Of course, these could be mesothermic or exothermic, but I'd sill imagine they'd likely prefer conditions that actual crocodiles enjoy.
I guess lizardfolk are specifically not warm-blooded, but I prefer my humanoid races to be warm-blooded; I think it's more realistic to have intelligent creatures warm-blooded, and find discussions of mesothermic to have this feel of arbitrary science intrusion in a world with huge flying lightning-breathing dragons. (I'm sure that argument first happened around 1974.) I'm not sure their underground dens would get all that cold; Cairo, the real-world equivalent of their location, never gets all that cold, and if we do say they're warm-blooded, that could keep cramped conditions quite warm.
Given all you've said, shouldn't they have a -2 Charisma?
"Charisma measures a character's personality, personal magnetism, ability to lead, and appearance." I'm not really sure they lack any of that. (I'm not a huge fan of Charisma in 3E/PF; it's a little hard to figure out what it means at times.) +2, +2, -2 stats are pretty standard, and I like the -2 DEX filling that slot. I could add a note being more explicit about the wide variety of skills they (or people dealing with them) could get a -2 (or -4?) to.
And why couldn't they learn arcane arts on their own or from whatever ancient wizards that used to exist where they lived?
In setting, they are basically a new race, 140 years old, of unknown origin. I don't think anyone can practically learn arcane arts on their own, so they'd need a teacher, and in this setting that would be hard to find. I wouldn't rule out a wizard saba'aeti, but there's none in setting.
What would make them adventure?
Same things as everyone else; wealth and power, or story specific things.
Thanks for giving it a look.