That seems like it could be reasonable for the bite attack.
I'll note that while the other movement granting features also only give a boost to speed per pair of limbs, they do boost the appropriate check for every feature. Thus it would be per individual leg rather than pair.
This would likely be an augment to the legs, so as not to overload it.
Might might either make it +1 per leg with the other things, or make it an inexpensive augment required the trample one.
Well, This could be an interesting idea. As an augment, the attack, damage, or both would be based on the number of legs with the augment (so it might be a base of 1d4 damage + 1 per additional leg with the augment), and the attack may or may not be boosted by other legs with or without the augment.
The ozodrin can carry others the same way any creature can. It's a combination of weight capacity, size difference, and DM fiat. After all, a small or tiny character could technically use a medium or larger ally as a mount if the DM allows it.
Similar to the above, this would technically be the equivalent of trying to pull yourself up onto the ledge using only 1 arm. If you're strong enough, you can do it, but most likely it is easier to use more than 1 limb or tentacle. It also would be somewhat harder given the increased distance that must be travelled.
As something of a side note. While the limbs would actually be modifying your base movement speed, it would be important to note that they would not affect other movement speeds based on your base movement speed (thus if you have something equal to half or twice your normal movement speed, you cant get a cheep increase to it using legs).
Also, it seems so far Markus Darkmind is the only one particularly interested in the PRC I'm working on. I'll give a hint though. It is not the eventually planned Maddening Choir I have a few ideas for, but rather shall be based on type instead of other classes, allowing it to be somewhat longer than the other ozodrin PRCs. Glimmar's
Owrtho