Ok, I'm a dork. I've been working on this for days. I just came back to my latest edited file and realized that just ONE of my model id fields had become blank somehow. So I'm not sure what was happening with the previous day's errors, but I think that upgrading to the newest version of EP4 helped, then I somehow deleted on of the model ID fields. Anyway, I just fixed that field, and uploaded/imported, and it worked!!!!!

Yeah, I'm a dork.....

Sorry for any confusion!!