I'm not sure of how long until the seed will be ready, especially since it depends partly on temperature and sunlight, but since you have a lot of flowers to work with, you can experiment a little. Once the protruding stamens dry up, it is usually 1-2 months until the seed is ripe. Look for the seed heads to become brittle and easy to break up. They may turn taupe or straw yellow, too.

Only a portion of the seedlings are likely to be curled, and the curling might not develop until the seedlings are hardened off to higher light intensities. On the other hand, some of the seedlings might be intensely curled, like the dwarf variety 'Curly Wurly'. For plants identical to the original 'Spiralis', let it grow bigger, and divide it.