Don't worry over the value of the two resistors. They're only used to create a midpoint and while lower values mean a little more current, it also mean less chance of noise pick up.
If you glue them down to a blank piece of PCB or similar, they stand a much better chance of surviving vibrations though. As is, they'll be stressed continually.
A blob of epoxy (eg. Araldite) covering both resistors and a little of the wires would be another possible life saver.