Radio is going to be what feels good in your hand....try some at your local hobby shop or from friends if possible. If you go the Futaba route, I'd recommend the 3PL over the 3PRKA if possible.
The Spektrum servo is junk. Those servos are known to go quickly, especially on the 1.0 on throttle. I'd get a Savox for Steering AND Throttle if you an afford to....or do Savox on steering and Spektrum on throttle until you can afford another or the Spektrum dies (Spektrum will probably die first).
The Jammin engines are Piccos and run at their best with Picco plugs. The .28 runs well with a Picco P5 Hot plug (expensive and hard to find) or Picco P6 Medium plug, but also works well with an O.S. P4 plug or O.S. P3 plug. (note the P ratings are different for different manufacturers)
Run it with 30% Nitro. Many engine manufacturers say they recommend 25%, but 25% is rarely sold in the U.S. -- you'll normally find people running 30% in their race engines and 20% in some RTR engines.
Regarding pipes, that is a key component in your engine's performance/tuning/runtime/etc. Give it a try with what you've got, but you may want to replace that if there are issues. Dynamite 053 is a good value, and you get the header and pipe.
Unfortunately, there are not any starter boxes that you can easily run multiple cars on. You'll have to change the 'peg' setup for each chassis. Most people have a box for each car.