Well, obviously not, psionics are only in one PH, and as an optional appendix, no psionic races or classes, and warlord is a controversial class (Henisoo's pet) that has only been in one PHB.
So, yeah, not even close to glaring or a real omission.
Like he said, that would be released to support one of their per year stories (Squid-Head Terror, or what-have-you), but he did mention books maybe being released outside of the stories deal, if there was demand.
I see no need for a penalty "to hit" for non-metal weapons (since 2nd Ed Dark Sun), but the -2 to damage for bone and -2 to damage for wood seems cool (obviously a minimum of 1 point on a hit).
Of course shields stack with mage armour, mage armour is like armour, where it sets your AC to 11+, shields just increase AC by 2.
Just like shields stack with Unarmoured Defence.
That is total ad-hoc house-ruling (denying a class feature), I know a lot of people that would be furious if a DM did that, way more than if he/she fudged a roll. I can see where you are coming from, but that is not playing RAW.
Yep, and The Mists of Ravenloft can reach Athas (there is an Athasian Domain of Dread: Kalidnay). And the Githyanki managed to get there. It is still not clear if at one point there were gods for Athas.