I jam quite a few tubers in a smaller space then you're describing, to prestart them before planting. There's really no issues in untangling the roots.. Just grasp each tuber and gently shake the roots free of its neighbor.

The only time it is a tad difficult is if you allow the roots to completely dry and they are root bound. If this happens, gently moisten and do your best to keep as much root mass with the appropriate root as possible. It's okay to lose some root, and probably helps the plant in the long run, as it will grow back UNrootbound!

Typically, I plant my tubers about four inches under the soil line. It varies, though. If the plant is really lanky, I dig the tuber deeper or lay the stem down horizontally (like tomato plants), using a brick/rock to upturn the top of the plant. The stem will root, and often provide more tubers in the fall.

Dahlias are fairly forgiving. They don't like pests and don't do well in cold, wet soil if they have no roots. Other then that, they will regrow sprouts or roots with no problem if they are knocked/torn off.

you've answered all my questions and i think i'm ready to rock and roll...thank you so much!