Single coils are brighter,but at the same time a bridge humbucker is too.10's I find to be a smidge darker than 9's,but I doubt that your strings are causing you problems.
What kind of amp are you using and what settings?
Any increase in bass will usually mellow any shrill treble... Is it the gain still shrill with your neck pickup?
Not enough info to troubleshoot.
From what it sounds like,you should adjust your pickups lower if there too high(the metal slugs being closer than around 1/15th of an inch is too high...I think).Check your amp settings and well...give more info.