It's too late for the onions in the six pack to bulb but they are usable at any time. Plant them and either snip off the greens for use like chives or let them grow and pull them as green onions.

A half inch seems deep (to me) for onion seeds but there are too many variables to know what caused them to not sprout. Try sprouting them in cell packs or flats for transplanting.

Rodney

Thanks, I'll try both those suggestions. :-)