hey dank, 1/2 oz is nothing to be ashamed of for your first grow! and it'll be the sweetest 1/2 oz you've ever smoked, trust me on that one
you got any pics of the whole plant, just to see how it's been progressing? also, are you planning a straight flush before you chop? they say about 8-10 days flush is ideal, plus you'll want to chop about 2-3 after the last watering so the plant is a bit dryer to begin.
as for harvesting at different times, i say go for it! you don't have much to lose... even if the plant "dies" after the main colas are gone, the remaining "dead" buds will still be fine and smokable.