Chainring bolts just come as either single or double, to fit single or double chainsets. Track nuts usually come in 9mm for the front and 10mm for the rear. It's pretty standard.
Correct. Omniums have very 'thick' spiders so you won't get enough thread engagement using standard single chainring bolts. I've also 'heard' that doubles will do the job but never tried it and don't use omniums any more.
Chainring bolts just come as either single or double, to fit single or double chainsets. Track nuts usually come in 9mm for the front and 10mm for the rear. It's pretty standard.