What kind of stuff is in there and is it doing anything negative?
Gas itself is a solvent and quite a good one so the chance of there being any sort of petroleum based gunk in there is pretty minimal. The water
traps are an excellent idea and pretty much a required part of your fuel
The reason your carbs are plugging up may not be related to the gasoline at all. Are you running your engine
frequently or has it sat for a few months? Gasoline does varnish
over causing the carb to gum up. A carburetor cleaner and a fuel stabilizer used right before putting the engine
Any rust in the bottom will be caught by the filter(s).
If your plugs are fouling it could be old gas, your air/fuel mixture or something else mechanical.
I don't know if cleaning
the tank is really necessary unless it has lots of rust, in that case, something else is going on and it may be best to replace your fuel tanks
before they rust through.
Be very careful when emptying a gas tank, at one point it goes between the LEL (Lower Explosive Limit), and the UEL (Upper Explosive Limit), meaning it is a bomb if there is any source of ignition. BTW, oil
tankers use an inert gas system to displace any oxygen in the tanks when doing this.