That is not an extreme amount of toe in. Looks fine.
...
Now, suppose the toe in really is too much. ... In a fairly short time (weeks), the trailing half of the pad (toward the front of the bike) will wear down faster, and the braking surface of the pad will become angled until the pad does lay flat under heavy braking. Think of using a pencil eraser while holding the pencil at an angle. In effect the toe in will self correct.
I agree that the toe-in seems OK.
But as for self-correction, you've got that half wrong -- the surface will tend to wear until the pad lays flat under their typical usage. The front of the pads may in fact wear more quickly, especially if the rider tends to brake gently. The effect of such uneven wear is to reduce the toe-in, so the brakes will start squealing again, first under heavy braking, then with more routine braking, etc. If/when that happens, it'll be time to toe them in again.
+1 on the notion of learning to do this yourself. As coupster notes, those Tektros are far easier to adjust than the old smooth post cantis of years past. The main concerns are 1) adjusting the pads to strike safely and 2) watching the wear line. If the front of the pads wears more quickly than the rear, you'll need to replace them when the front gets thin even if the rear is still nice and thick. C'est la vie.