Whether my volume is high or low, and even when I am over 20 feet away from my amp, turned away from it, and my left hand is over my strings to avoid any errant noise, I seem to have a huge problem with piercing shrieks.

I'm running my Schecter hellraiser fr through my boss bcb60 pedalboard into my 6505+

Guitar > Pedalboard [Boss TU3 tuner > Ibanez TS9 tube screamer > Boss DD20 digital delay > Boss GE7 EQ > ISP Decimator] > 6505+

My Tube screamer can't be completely on drive or level without earsplitting pain [which isn't that big of a deal, I like keeping the level low, but I would like to use more of the drive knob. My DD20 doesn't cause much of a problem. My GE7 whenever it is kicked on, particularly when my tube screamer is already on, is a HUGE problem. Even with my decimator about about -45 db which is exactly where i want it, I get horrible feedback and a bit of hiss. After about -50 on the decimator i lose a bit of sustain and I don't want to jack up on the knob past -45.

I don't use the effects loop on my amp but to be honest I bought it used and don't know how to properly hook my effects up that way. Maybe that's my problem, or maybe I have the pedals in a bad order? I also have a Boss CE20 chorus pedal coming in and I'm afraid I'm going to deal with even worse noise.

The good news is that today I spent a bit of time toying with my amp and I found a setting that gives me a really good tone, and minimizes the hissing to almost silence, but I'm still dealing with feedback.

So, forgive the novel, but I figured I should give all the information that seems important. Hopefully you guys can help me out as always.