@Easy Slider you're kicking the board away because you're skating up to the stairs with the idea that since you've never done the trick there before, then it must be difficult, except the bigger of deal we make about skating the harder it is. The downhill thing you think helps doesn't sound ridiculous at all (being scared of a void I'd say is natural), just I honestly have no idea how you're making work - stairs with a downhill run-up have always been the most difficult type I've found to skate, specifically because then you can't see the spot. I totally know what you mean because we have one particular, otherwise perfect 6 here no one skates because it's built exactly like that - messes everyone up. Personally I think I'd rather take uphill run-up than downhill, I find it that awkward. I think you should embrace the spot and not deny it, though, that rarely works.
Assuming you have a good flick and catch on your kickflips, you should try and look at the 3 you're trying to skate as no different from your usual 2 at all - just consciously blank out on the difference, or maybe in fact consider it from all possible angles including 'well I've done this before, it's a kickflip going down curbs except instead of two curbs there are three but what difference does that make and who's counting'. Technically, the only difference will be slightly more air time after you've caught the trick, which you should know how to handle if you can ollie the set, and so as long as you form the kickflip right then there's absolutely no stopping you but yourself, mentally.
But then forming the kickflip right shouldn't become an obsession either, otherwise your brain will focus on that as your main goal and then bail, resulting on good catch then kick out (or instant miss on the pop as soon as one run-up feels off). Your 'obsession' if anything should be on your ideal rollaway, what you want is ride away past the stairs by the means of a kickflip (which is a maneuver you know how to do) if that makes any sense. Don't micromanage the kickflip part and how it's supposedly challenging, focus on clearing the stairs with one as part of a bigger picture. You have control over when your concentration should start and stop.
Or if your brain really insists on being wired in a way that messes you up on them then maybe you need to get more consistent and fluid at the trick. I know I don't really try anything down stuff that I can't maneuver and control, say, as easily as up a curb, and as a kid I had to get my kickflips to that stage too before I could do good ones down gaps. When I first learned kickflips (pre-Internet), they were completely chicken-legged and mobbed and doing those down anything was never going to work, and so I essentially had to relearn them entirely with the ollie, then late extra flick technique and now those started to work, because they weren't anything special anymore and felt as comfortable as the logical extension of a normal ollie.
Rambling a bit on a rainy Sunday morning, but I hope this helps!