1) Wade, use a light house mix and downstream it, and you should be fine. Get the roots of the IVY, and any other plants plenty of water FIRST, then Pre wet the ivy foliage before applying, then keep wet as you keep applying. That IVY is a pretty strong plant and you shouldn't have any problems. Also, do the job in the early morning, like 8;00am, this will help prevent the sun heating the ivy up. AS for the ivy on brick, use an adjustable wand, but let your customer know you cant guarantee 100% that a leaf or vine may not get damaged. I always let them make the choice, if they expect the ivy to be as is when I am done, then the surface behind will be the same.
2) For the rear, use your long range soap and rinse tips, apply from bottom to top, let dwell, then rinse. If you don't have the right long range tips, get with Paul or Russ and they can get you the right ones for your machine. F-13 should not be needed on this job.
3)Your price of 300$ seems to be in line. This shouldn't take long at all... 1 hours to 2 hours at most for you.
Call me if I can help any further