flower until 50-80% of the hairs turn dark (orange or red, most likely) or if you have a decent scope, until 1/3 of the trichromes are clear, 1/3 are milky, and 1/3 are amber (that's optimum for my grows; some growers like 50% milky, 50% ambery)
in regards to the bugs, neem oil is the best choice for serious growers, but it can be expensive depending on where you buy it and how much of it you buy, so I like to use a mix of 50% water (at least) and 50% rubbing alcohol (at most) if that doesn't work, i've heard that a teaspoon of dish soap per gallon of water seems to do the trick for most bugs also, but i have not yet tried
i just did the water/r. alc mix on my own grow (check out my journal) and i haven't seen any bugs since
if you're careful, you may even want to pick the seedlings, wash it off, and transplant it in another pot of soil, but this can be a gamble and you should try it only at your own risk