Doug, you should get a more recent soil test to see what the ph is now; it has probably increased. If you get the soil test from your local USDA service center it will be for the specific plant you want to grow. And, will tell you the amount per acre for lime, nitrogen, phosphorous, and potassium.

As for the depth of topsoil, it depends on what you are growing. Each plant requires a different amount of topsoil; because of the depth and surface area of the roots. You mentioned that you have a rocky, sandy, loam. But do you know that it is shalow because you are going to bedrock, or hitting a good size rock that is floating in the soil itself? In sandy loam soil there need to be sufficient water to keep the roots hydrated during a dry year so keep that in mind when choosing a plant to grow. Good Luck.