I am glad that the OP was not hurt to bad. I have a friend who ran his hand through a dado set, it was UGLY!

First off, you should never try to back a piece out of the spinning blades for a stopped cut, or in your case a stopped dado. Shut off the saw and wait for the blade to stop. A shop that I used to work in the owner would lift his sheet off the dado set for a stopped dado, but that didn't look real safe to me.

I heard you mention that your dado was not uniform in depth. the fix for this is easy. In fact this is how we did it in that same shop, and I still turn to this technique regularly in my shop. After roughing your dado on the saw you can chase it using a Whiteside 3000A or a 3000 bit in a small router. This will give you a uniform dado depth with a nice flat bottom. If you find yourself turning to this with any regularity then you might consider having a dedicated small router setup for this task.