I didn't read everything so if I repeat something, I apologize ahead.
First, and this may be controversial, ... but I am not a fan of squirting anything, even silicone oil, in the gun in the hopes that it will do any good. The tiny amount of lube you should use during a rebuild is all that needs to be in there. Just my opinion over many years of pcp use and building.
To control moisture, you first need to make sure than your fill line, filter, and anything else in line on the way to the gun should be below the gun during the fill process. This keeps moisture from rising up into your gun. Cotton filters do help by blocking liquid flow. So they do help some. Also your environment needs to be fairly low RH, ie 50% or less, so a dehumidifier might help in the room where you fill. Also, pump for short intervals, less than 10-15 minutes and then vent the lines.
If you use a pump that is conducive to it, and you just can't get the moisture out, the real solution is to feed your compressor nitrogen at low pressure. It's not at all expensive and is the magic bullet for moisture problems. All you need is a way to pipe a line from a 40 cu/ft N2 cylinder with a cheap regulator to you compressor, run it at 5-10 psi and done, NO MOISTURE.
I live in WV and it can get hot and humid in the summer, and I fill in my garage, which is usually open to the outside most of the time. If I'm careful, I get no moisture in the gun and only a small amount in the compressor and lines. The fittings do runs a bit inside the fill line and block, but never gets to the gun.
One important thing is that you should open EVERY pcp cylinder on a, I don't know, yearly basis to inspect the inside for corrosion. This is the best way to KNOW if you have a problem.
I have used Nitrogen for about a year now and will never go back. No filters, (except for a cotton debri filter) and no maintenance to mitigate moisture. It alleviates all the hassle of filling pcp rifles. If you count the cost of changing the moisture absorbing media as often as you really should, N2 looks pretty good price wise.