I believe that I can be of some help here with respect to two issues based on experience.
As you obviously researched the literature I am fairly certain that you are aware that the snails were imported via your plants.
"I have been there and done that": you can probably barely see into your tank due to the snails and their egg sacks on the walls of your tank.
I researched the literature and decided to purchase 7 yoyo loaches (one of Blue's options) as my tank is 110G. http://www.aquahobby.com/gallery/e_lohachata.php http://animal-world.com/encyclo/fres.../YoYoLoach.php http://www.badmanstropicalfish.com/loach.html
I live in a community in West Texas where purchasing fish such as yoyo loaches is not possible and I purchased mine on line approximately 6 months ago. http://www.aquariumfish.net/catalog_...es.htm#loaches
Mine were very small when I received them.
4 to 6 weeks later I had much larger yoyos and no visible snails.
I have a wet/dry filtration system and even now I find very small snail shells on the mechanical filtration media (best guess is approximately 10/week) even though none can be observed in the tank.
I am also "into angels" and have 7 in my tank ranging in age from 5 months to 7 months and in size from 3 inches to 5 inches.
I have raised these angels from dime size.
I have 7 sterbai also which are somewhat boisterous.
The yoyos and sterbai also play with each other.
I have not observed the yoyos' and sterbai' playing bothering or stressing the angels and, as indicated above, the angels are growing quite well.
One last note:
I researched the literature extensively before I purchased my aquarium.
The literature indicated that a 30" deep tank was preferable to a 24" deep tank in order to raise angels to their full size.