My car does not have an automatic transmission, so I did not have to remove the dipstick tube. I expect, however, that it is indeed where the ATF is coming from. I wouldn't worry too much about it. Take things one at a time and get the engine back together and running well first.
Oh yes, did you remove the radiator. The cooling lines that connect to the radiator may be your leak. I'm sure you can work it out without too much trouble.
I have not mentioned that the rocker arm stands should go back into the same positions from where you took them apart. This is so that the cam followers will be on their original lobes. I'm sorry I did not mention this before you took everything apart.