The way the t-maxx tank is shaped tends to cause the last 1/4-1/5th of a tank to lean out a bit. So that power surge at the end is pretty normal, but not really anything to worry about.
I used to break t-maxx tanks constantly and ended up fitting an OFNA rectangular tank that was uniform in...
Well... like you said, there are schools of thought on that... but with fuels having synthetic and castor blends in them these days, the oil in it can handle higher temps safely.
I tend to try and tune so it performs well, runs ok, idles, starts, etc. I check the temp so I know where it is...