I don't know about your other problems but the corner lights may never work properly with led's. As my memory serves me the corner lights are wired between the headlight switch and the turn signal bulb. with the headlights on the corner light is grounding through the turn signal bulb so when the turn signal flashes on you have power to both sides of the corner light and it goes out. When the turn signal flashes off the bulb then grounds through the turn signal and comes on. Inversely when the head lights are off the corner light powers through the turn signal bulb and grounds through the headlight switch so that when the turn signal flashes on it powers the bulb and it comes on, when the turn signal flashes off there is no power to either side of the bulb and it goes out. I am not familiar with the resistance through an led but it is entirely possible that the corner light can not get the necessary ground through an led and therefore will not work. I am not 100% sure of the wiring on your truck but this is how I remember them wiring. With regards to them hyperflashing, large trucks, I am speaking of tractor trailer units used to have a motor driven flasher in them. It plugged into the same socket but was as I recall about an inch and a half cube. It had a small motor driving a mechanical switch so that the flasher never changed speed regardless of how many bulbs were on it. I dont know if they still use them or if they have a different system but they by necessity need to have some kind of flasher that is not sensitive to adding or dropping trailers and the addition or subtraction of all the additional bulbs. This would cure the flash rate problem.