does anyone recognize what this is?

Probably cabbage worms. Look under the leaves early in the morning to see if you find green caterpillars; the adults are the white cabbage butterflies. Use Bt spray or dust to kill them (Bacillus thuringiensis)

Bt is almost a requirement for growing anything brassica. Those cabbage worms, or the striped ones, are terribly common and devastating.

are they ready for picking? how developed do the top most brussel sprouts need to be?

looks great! Just judge how big you like them?

ok i had quite a few! the plants made it through the winter! but how do i regenerate a new plant? i need to get new growth to pick. is each sprout seed to plant?

Eat those sprouts before they leaf out!. No seed in sprouts. I expect seed from the flowering top when it appears