Compressed air is your tire's worst enemy. Air is about 78% nitrogen, 21% oxygen, and 1% other. Nitrogen is inert, non combustible and non corrosive. Oxygen, on the other hand, is immensely destructive to rubber and other tire materials. As soon as a tire is manufactured and exposed to air, the effects of "oxidation" begin to deteriorate the rubber. Over time it loses its elasticity and strength, just like an old rubber band you've probably found around your home. This same process occurs in tires inflated with air as the oxygen attacks the rubber molecules, working from the inside out, until the oxygen, and its destructive properties, permeates the tire structure and ultimately the tread.

  Yes. Nitrogen will help maintain proper inflation in your tires and reduce the number of faults detected by the TPMS. 
                                            

No. Nitrogen is an inert, noncombustible, nonflammable, non-corrosive gas. In fact, those are big reasons why nitrogen is used to fill the tires of vehicles that push performance limits under extreme conditions, including Race Cars, Aircract and Heavy machinery.

 Yes, While it's often referred to simply as an "alignment" or "wheel alignment," it's really complex suspension angles that are being measured and a variety of suspension components that are being adjusted. This makes an alignment an important suspension-tuning tool that greatly influences the operation of the vehicle's tires.

Out-of-alignment conditions occur when the suspension and steering systems are not operating at their desired angles. Out-of-alignment conditions are most often caused by spring sag or suspension wear (ball joints, bushings, etc.) on an older vehicle. They can also be the result of an impact with a pothole or curb, or a change in vehicle ride height (lowered or raised) on any vehicle regardless of age.

Incorrect alignment settings will usually result in more rapid tire wear. Therefore, alignment should be checked whenever new tires or suspension components are installed, and any time unusual tire wear patterns appear. Alignment should also be checked after the vehicle has encountered a major road hazard or curb.