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Let me be the first one to say that I have absolutely no clue what the above is talking about and I doubt you do.
I wouldn't try discussing anything with an expert of your caliber... I'd be fighting with an un armed man... The regulator can't get hot on USB power... it isn't used, that's what the OP-AMP does it turns on a fet when there is no DC power applied... connecting the USB power to the board... 5V directly from the USB power... this also seems rather strange consiidering your hardware list and I quote:
To give you some sense, I have a board with the following load: 3 avrs, 1 pic, 1 1602 lcd, two hc132 oscillator (14Mhz + 70k), two hc04 oscillators (4Mhz + 12Mhz), 1 4-digit 7-segment led, 1 25Mhz oscillator, 1 14.7Mhz oscillator, one rgb led, 9 bright leds, 2 7-segment leds.
Powered from a 15v Verizon phone adapter, regulated down to 3.3v, the linear regulator (to220, no heatsink) is lukewarm. I think I measured my current consumption at one time and it was around 50ma.
50 mA would cause a small heat rise in the linear regulator a Backlight @ ~150mA would make it quite warm, uncomfortably so but not noticeable if operated from USB power as the regulator wouldn't be in circuit. I was really beginning to wonder if you would ever realize that... Small Detail. And Yes, I have forgotten more about linear regulators that you will ever learn, I made my first discrete 40 years ago... from the style of your writing I'd put you at under 30... well under, so don't even try to question my experience or knowledge until you've walked a mile in my shoes.
Bob