incredible score, nicely done!! i doubt you're having any skill issues, there's just genuinely more work to be done on making bullets more readable. in particular, once they cross the player's plane, i think they need to get dark immediately instead of just semi-transparent. i also think the enemys' habit of directly shooting through the screen origin, especially salamanders, is not an ideal bullet pattern, kind of a worst-case for readability actually.
i'm glad you got into it enough to discover that speed strategy! i'd love to see a video of it if you happen to have one on hand (you don't need to go too out of the way for it though). you're one of the most valuable types of playtesters if you can find exploits... though it's not an exploit if it's fun! my thought, just from your description, is that enemies should fire at least a small volley of bullets before exploding to a combo shot -- that way you can't remove bullet dodging altogether via mouse flailing alone (if the game is updated later this would be combined with better bullet readability). would you agree?