Hardiness is still more a language choice for Constitution, not Strength.
None are listed. Does this mean that the Theg see as humans?
You still need to clean this up. It's mechanically sound but looks really clunky in its set up.
Ancient Netherese Patronage
This is worded clunky and it's hard to really understand what it does. I'd suggest wording it like, "Theg receive a bonus on Knowledge skill checks equal to one quarter their total hit dice and may make all Knowledge skill checks untrained". That's half as good as the Bard's Bardic Knowledge class feature and should be all right as a racial class feature.
What is the "Improved Racial Familiarity" feat? I can't seem to find it anywhere.
And what does the historian magnet bit have to do with anything mechanically?
There are no racial favored classes in Pathfinder.
The weight modifier is the same thing as the weight multiplier. You roll the height modifier and multiply it by the weight modifier to get how many pounds to add onto the base weight.