4. So if I want to take a break from the post Destiny universe and read the DS9-R before going forward. Should I do it right away or is there any of the new books I still can read withour spoiling anything. I'm mostly thinking about the Voyager relaunch (I'm at Children of the Storm now) and TTN: Torrent Sea and Synthesis.
I know I'm a little late coming into the thread, but you should read the DS9R as soon as possible. It really was the start of the modern TrekLit, and it did set up a lot of threads (with the biggest being the Andorian crisis) that have continued into the most recent books.
The Voyager books take place mostly in the DQ and are a little behind in the timeline, so other than a few fairly vague references they are pretty much outside of all the stuff going on in the other 24th Century series.
5. And how about Vanguard. Do I gain anything by reading it before I go into the Typhon Pact books? The Tholians ambassador has mentioned the crimes of the Taurus reach and I have no idea of what those are or if it's a big thing in the storyline.
The Vanguard books are amazing, and some stuff introduced in it does play a role in the current books.
Neither series is absolutely necessary to understand what is going on in the newer books, but you will get a little more background from DS9R and VGD that isn't in the current books.
6. Apart from Vanguard, DS9-R and A time to... , are there any other pre-Nemesis necessary reads? According to yourselves of course =)