Except for the stage 3 boss, it doesn't really get too bad, stage 4 and 5 are a bit "leeeeeft ... riiiight" like you say, so you just do the same but the bullets are a bit quicker. It doesn't take too much adjusting.
If it makes you feel any better, I was as surprised to see that little prick as you clearly were! I must mop all those up with my wide shot before they get a chance and you must have left a straggler what with you playing it safe and focussing more than normal. Plucky little fella, he nearly had you!
Beat my stage 1 score, not that we're keeping tabs, but it feels like the night wasn't entirely wasted!