25 Hz rate to be used as a sampling uppdate
That seems to be awwfully slow. I would go for some hundereds of kHz (sample every period).
I do not know how fast your A/D is, but I would run the regulation as fast as the A/D could handle. Another thought: you could really speed it up if your processor has a D/A and a comparator. Are you sure that you sample at the same state of the switcher every time and thus not have sampling ripple. It would be accurate if you - with sample and hold - used the average of Vout max and Vout min (your switching knows when that is).

The Timer 2 is programmed to produce a pulse train out the T2OUT pin. This will be a software variable frequency with a fixed 20 uSec high going pulse
That may be a problem for your magnetics. Also this method tends to be very bad at low loads.

However I have found that if the load on the output varies over time then the high voltage may not be able to get up to the level desired.
That is because a switcher controls watts, not volts.

Erik