The curious coincidence of RH just happening to buy lightbulbs on that particular day and just happening to take them to the car and put them in without bending down... Is another thing that I see as completely irrelevant. If you think he murdered his son then you make it into something suspicious (he was obviously going to check if his son was dead yet, for some reason!). Me, I just think he needed lightbulbs. LE checked, and he did indeed need lightbulbs. And it's tragic he never noticed Cooper at that point, but I don't see it as evidence of malice murder at all.
Same with him apparently taking an odd way to the cinema. If you think he's guilty you can come up with some motive for him doing that relating to murder, but I don't think it's evidence of malice murder. There are loads of reasons why he could have taken that way.