I've used LM2576 twice and never had problems with it. Very easy to get it work.
At the first time I made some tests, and with 2A it does not heat much.

Have you tested with some other load than your servos?

.........I think for a 1k series resistor anything between 10k and 100k should work fine.

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The Aussie Shield: breakout all 28 pins to quick-connect terminals

I disagree. If the 1k resistor is changed to 100k and the other one is 47k, then the current from the output is 34 uA causing only 1.6 V to gate. With 1k, the current is 0.1 mA and gate voltage 4,9 V. Much better.