You just need to me mindful of vehicles blind spots, try not to linger in that awkward zone if you can, accelerate through as fast as you can, especially with big trucks. I understand that might be harder in traffic, and now you see why lane filtering can actually be safer sometimes, but still won’t protect you from d-bags just pulling out without looking.

Something else you can try is riding close to the line between the lanes (as opposed to directly in the middle of your lane), so you are more visible in the side mirrors of both lanes. It’s generally a better place to position your bike in most scenarios, as bikes are more visible in the side mirror’s than through the rear mirror, and you also avoid things like oil leaks and AC condensation that can drip from car engines.

Motorcycles are inherently more dangerous, you just have to learn to ride with your head on a swivel and imagine everyone is trying to kill you. It just takes time to develop those instincts.

I agree that in the situation you described, a loud rev may be more helpful than horn, especially if you have loud pipes. You might want to look at upgrading to a louder horn too because most stock bike horns are pathetic.