I recently bought a 1992 Kawasaki Ninja 250 to use for track days.
It's in pretty good condition and only has about 3000 miles on it.
What I am worried about is that the gas tank was VERY rusty when I
bought it.  I spent hours cleaning it out by shaking it with various
metal nuts and bolts in it as well as filling it with muriatic acid
(hydrochloric acid) and letting it soak and then rinsing it out (I did
this 3 or 4 times with different strengths and different time periods).
I managed to clean most of it out completely so I could see the bare
metal on the inside of the tank - there were some patches of rust left
though.  However the tank starts to get surface rust pretty soon after
emptying it.  The fuel petcock has a very fine filter screen on it that
would prevent any rust particles of any real size from entering the
carbs.  Just to be on the safe side I added an aftermarket fuel filter
in the short hose that leads from the tank to the carbs.  When I turned
it on and let it run for a little while I realized that the aftermarket
filter wasn't attached very well to the hose and and was leaking slowly
from both sides.  When I removed it to put on some clamps to secure it
better the little bit of gas that came out of both sides of the hose
looked to be a little dark like maybe some super fine rust particles
where able to make it through or maybe the rust disolved in the gas to
create a gas/rust solution of some sort.
Now that I have finished explaining things here are my questions:

First of all, will incredibly small particles of rust damage an engine
or clog the carbs?

Am I just imagining things?  Should two filters remove any rust
particles that could enter?

If rust does dissolve in gas to create a solution that would pass
through a filter, will it damage the carbs or engine by accumlating on
valves, coating cylinder walls, etc?

What would be the recommended course of action?  I have invested a lot
of time into cleaning it (probably over half a days work) and don't
want to write it off.  I also only spent about $500 on the bike and
wouldn't prefer to spend $150 to $250 on a good condition tank off of
eBay.  Does anyone have a recommendation for a cheap sealant or
something similar if rust is getting into the engine/carbs and causing
damage?  Will I have to remove those last spots of very stubborn rust
somehow?