Easy solution for the black backpack, go to an arts & craft store and buy some duct tape. I put some strips of construction orange duct tape and prism reflective duct tape on my backpack.

With lights, I was surprised to find out that using a steady headlight during low visibility daytime got the attention of cars a lot better than a flashing light.

As far as light brightness, 700 lumens is the standard for car low beams. I've seen lights for sale that are brighter, but that would be like using your high beams when there's oncoming traffic which is both a jerk move and I think illegal. If your light is 700 lumens or slightly less, the angle may be too high. Or the driver was just whiny.