Basically C is the limit, you violate C in any way from any reference frame and you violate Time. Light loves being an invariant.
This depends on how you define the phrase "You violate Time".
Any violation of c from any reference frame will, by definition, violate causality from that reference frame. If the Priceline Negotiator starts a self-destruct countdown, and 1 minute later his starship explodes... if the starship is moving faster-than-
c toward any reference frame, an observer in that reference frame
will witness the explosion prior to the countdown. This is, by definition, a causality violation.
However, it is much less clear whether a violation of relative causality necessarily leads to "time paradoxes" such as the Closed Time-Like Circuit (CTC) or Grandmother Paradox (GP).
In the simply-defined case of tachyons (a particle that
must exceed c in
all inertial reference frames), grandmother paradoxes are guaranteed - all you need is a tachyon bouncing between two other particles that move slightly-slower-than-light. That tachyon will bounce back to its sender
before the initial message was sent - a classic Grandmother Paradox.
Wormholes are tricky because wormhole physics is not well defined, and there are no logical limitations on how wormholes could interact with time. A single wormhole could connect "Earth, year 2015" to "Galactic Core, year 2015 (Earth reference frame)"... or it could connect "Earth, year 2015" to "Galactic Core, year 1,000,000BC (Earth reference frame)". The latter would
absolutely represent a time paradox, because you could then fire a photon torpedo at Earth and destroy the planet a million years before you were born.
Requiring a wormhole to go outside the Hubble volume (ie Observable Universe) doesn't prevent the possibility of time paradoxes, or even the possibility of FTL travel within the Observable Universe. All you have to do is take one wormhole from Earth to Universe B, then take a second wormhole from Universe B to Epsilon Eridani. At that point you're well within photon torpedo range of your grandmother.
IIRC there's a Stephen Hawking hypothesis out there that says that closed time-like circuits (CTCs) may inherently define themselves out of existence because they have infinitely high energy and therefore infinitely low probability. (I'm not quoting exactly; this is my limited understanding of the physics) No matter what type of FTL travel you propose, if there is any possibility that a virtual particle intersects with its own past, the probability of that particle history will become zero so it won't happen. This could allow an infinitely large network of "wormholes", but their space-time reference frames would seem "infinitely finely-tuned" so that it is impossible to use wormholes to interact with your own past.