Personally I would recommend losing the shampoo altogether & going with a body wash or another shaving product instead. As I've mentioned to another guy, shampoo is mostly detergent with whatever crazy stuff that the manufacturers throw in there, and is meant just to clean hair not your scalp, it isn't formulated for that and any shampoo that says it is, is probably just trying to sell you something.

It sounds like a lot of the stuff you're using is exacerbating the problem rather than fixing it, its that same vicious circle that I went through with my facial acne when I was a kid, I used all the HARSHER THAN HELL scrubs and estringents, plus all the bezoyl peroxide gel I could use, which just dried out my skin so badly that the sebacious glands in my face went to warp factor 8 which just made my skin greasier and greasier and the zits got worse and worse. Then a dermatologist who WASN'T in the pocket of big pharma suggested that I use this revolutionary product called "Warm water and a face cloth." Within a week of just washing my face like that, my skin cleared up to the point that I didn't need anything else anymore.

I use Old Spice Red Zone for both cleaning AND shaving my lid, (It has lots of moisturizer in it so it works great!) plus you might want to invest in a manly loofah sponge to scrape all the dead skin cells & other detrius that builds up on your melon.
I use the loofah both before and after I shave & lemme tell you it feels AWESOME.

Ok I'll shut up now.

Consider a mild anti-bacterial acne soap--something like Cuticura.  And, wasy your head at least two to three times a day.  Another villian in this, pillowcases.  Change them regularly, not less than once a week.  Generally keeping it clean, keeps it clear.  You might also consider the possibility of an allergy, think about the hypoallergenic products.  There are loofha pads at WalMart, less than $3 that really help gently keep the follicles open and clean.

I recommend using a hypoallergenic shaving cream --such as Aveeno.  It's helped me tremendously.  Also keep the number of products you use to a minimum.

After I switched from Headslick to Aveeno, my skin cleared up by about 75% to 80%.  I did have a couple of flare-ups, but they were much milder than they had been.  During one of them, I decided to use some extra caution and avoid getting any kind of shaving cream on top of my dome.  I pulled out my old electric Remington; I haven't used it in a long, long time and it needs new blades, but I gave it a shot anyway.  I used it on top of my head and then lathered up the fringe area with Aveeno and shaved with the blade as normal.  This resulted in even more of an improvement.  I've been doing this for the past 10 days or so.  I've had one or two mild flare-ups that cleared up within 24 hours, as opposed to a week or more in the past.

It's not a good solution for everyone, but if you're as sparse on top as I am, it may be an option.  Even with the worn blades, I was able to get the top pretty smooth.  It doesn't stay smooth as long at does when shaved with a blade, but it's a small price to pay to avoid a breakout.   Rather than invest in new blades for such an old razor, I've ordered one of those Conair Clean Head razors.  It hasn't arrived yet, but once it does, that's what I'm going to be using to keep the top of my dome free of the peach fuzz.