I know the 'legal' standpoint and I still use the 'proper' Codex myself, but in the big bad wide world there is a lot of debate going on about what has precedent - the book or the pdf. Some Tournaments are going by the pdf, others say the book, and the same goes for individual opponents who want to play the badass and deny the Codex and/or the pdf depending on what suits their own lists.
GW stuffed up when they basically said 'decide for yourself which one you use and come to an agreement with your opponent'.
They also said that the pdf does not supersede the codex:
"The other point that seems to be causing the most confusion is whether or not the PDF versions supersede the printed versions. They don't: you should feel free to continue to use whatever resources you have available to play your games with; the PDF does not overrule or invalidate the printed Codex book. " Don't see how there can be any argument given that particular statement.
As for needing allies, no, but it is nice to have some access to a psychic hood.
To ABT. DH units cannot share their own dedicated tranports, they are the only army that this still applies to. Yes, if you take an IG platoon and give it chimeras, then the DH units can use the IG transports. And yes, termies can ride in chimeras, they just take up two spaces.
However, as the others have said, allies are supposedly going away. Someday. Probably someday soon. So don't get too attached to the idea.