If your going to divebomb then imho 1k-4k is too low for starters. More altitude before drop equals more time to adjust for drop during the dive which leaves a better chance on hitting accuratly. As a general rule I start my dive at least 8k over the field and in most instances around 9-10k. I usually dive in at greater than a 45degree angle and chop my throttle and flare to cut my speed way down before the dive so that I do not have too much speed when I drop or else you risk the chance of not being able to pull out in time or in some cases being damaeged by your own bomb-blast. While in the dive I adjust so that the target is between the nose and crosshairs and as soon as I'm lined up and need no further control inputs I salvo and pull out. You know your lined up properly when if you did nothing you would auger on target.
Hope at least some of this helps. Remember, everything in this games takes practice. Try not to get frustrated and give it a few runs offline or in the TA before you try it online. Good Luck