I had a 77* on that drop in the middle of Onslaught, exactly 1* past El Toro

lol
The reason I went with that value was to have the steepest drop possible with that height. That maximized my airtime and pullout g's, and also had the great side effect of making the drop steeper than El Toro's. There were several other reasons for having a steep drop like that in the middle of the ride, but those were more related to Onslaught's layout than to the forces.
Anyways, yeah 80* is a perfectly realistic and awesome angle for an Intamin woodie drop. Intamin could have made El Toro's drop steeper without increasing the magnitude of negatives for the back row, and you have extra height to work with, so it's fine.
Your ride as a whole looks like fun, but doesn't look too original so far, and I think you should make sure not to have too many simple transitions, like those that start a turn at the steepest part of a drop. Definately try to switch some stuff up in the next few elements, because otherwise you'll have another slightly changed ripoff of El Toro and Colossos (which is realistic too, just has been done a million times). If you're going for that feel, definately mention in your description that you're trying to make something that you'd really see in a park, and also try not to overdo the layout in length or number of elements, especially with an Intamin since they tend to stick to relatively simple yet thrilling designs, with some exceptions ofcourse.