The Surprising Ways Mars is Hostile to Life

so what I'm gathering more and more is that, in order to Terraform Mars, we need to give it a moon (same for Venus).
A larger moon than it has; enough to disrupt the core and get it churning again, enough to ease Mars's wobble, and maybe also thereby help "grow" an ozone layer. A more active core means more vulcanism, means more gases into the atmosphere. Genetic engineered plants, or artificial photosynthesis factories, could pull carbon out of the atmosphere and increase the oxygen content. Mars would have to be richer in oxygen than Earth since it doesn't have the nitrogen we have, but too much would be poisonous to us, too. 
Perhaps a series of controlled impacts from icy moons of Jupiter or from Saturn's rings (or icy asteroids if we could find them) could both thicken the atmosphere and add inert gases such as nitrogen to its atmosphere. Could also be good practice for when we scale Vesta or maybe Io into Mars orbit (sorry, Titan, with its petrochemicals, is bound for Venus...)
Push come to shove, robot freighters could scoop-dive the upper atmosphere of Jupiter/Saturn and drag it back to Mars (probably frozen into a solid by the time it gets there, anyway). Detachable, replaceable cargo containers that could just be dumped from low orbit, maybe.