Nicodemus:
1: Forgeworld made a book (ToC) which includes a functional Chaos Dwarf list, for the new units?
Malorndk
As stated, the book is called "Tamurkhan: The Throne of Chaos". The Chaos Dwarf army is specifically called "The Legion of Azgorh", or LoA for short. At the risk of putting too fine a point on it though, the list doesn't describe all of the Chaos Dwarfs, and it's relatively clear from the book that the Legion of Azgorh are just one faction - that being the troops that fall under Azgorh's control (Azgorh is a Chaos Dwarf).
2: The new book isn't official, but it's widely accepted in stores and at turneys, though it co-exists with Ravening Hordes?
Malorndk
Correct. Not official, but exceptionally well accepted. And yes, even though it co-exists with Ravening Hordes. They were very specific to point out that the LoA doesn't replace any pre-existing CD list, it's just an alternative.
3: Its possible to mix the units from ToC into the ravening hordes list, by treating "The great host" as "Ravening Hordes - Chaos Dwarfs" in this errate?: http://www.forgeworld.co.uk/Downloads/Product/PDF/t/tamurkhanQA.pdf
Malorndk
This might be a stretch. The LoA list is setup that you can take it as a stand-alone list, or you can take them in a WoC army. Alternatively, you can use the LoA as "Contingent Forces" in a Chaos Great Host army (see p142 in the Tamurkhan book), or as allies in a Grand Battle (see p132 in the BRB ).
Your best bet for getting your Deathrockets, Earth Shakers and cheap Hobbos fielded would be to either a) play casual games where the group doesn't care if you do this, or b) play games that make use of the Chaos Great Host army rules.
Without giving away the rules, the gist of the Chaos Great Host army is that you
must select units from at least two or all three of the following lists: WoC, Beastmen, Daemons. For 99.9% of Warhammer players these three lists sum up 'Chaos'. For us CD players we might be asking, what about RH and LoA? Well, the Chaos Great Host rules doesn't give any other details, it doesn't say you can't, but my impression from reading that section is that the aforementioned 3 army lists are the only 3 you should be considering. In which case, the LoA units come in the back door via WoC. Upshot - you can't have a free-for-all with the LoA and RH lists and take what ever you want in a Chaos Great Host. Furthermore, there's no obvious mechanism for getting access to the RH list. Sure, just about everyone here on CDO would likely agree that the RH CD list should be grouped with 'Chaos', but it's basically been quietly forgotten and orphaned in 8th ED. Anyway, I'd avoid the whole Chaos Great Host rules as they're quite cumbersome. Oh, and those "Contingent Forces" I mentioned about for the Chaos Great Host army, it's spelled out that way with capitals on p167 of the Tamurkhan book, suggesting that it's a rule and they say to refer to p142 in the same book. Unfortunately, there's no mention of these "Contingent Forces" in that section that I can find. The closest thing is the subheading "Forces of the Chaos Host" which lists the 3 Chaos lists I've already mentioned above. Go figure.
Another route to get access to the RH list would be to try to get it on to the list of allowed rule books for your gaming group's Storm of Magic games, and then summon some units in!
Hope this helps.
~N