Have you verified there is no air pocket in the system?
I always turn on the heater on high, let it heat up to temp. Verify rad is full.
The divider plate is also a good suggestion.

What type of starter are you running? Is the battery discharging or is it just having a hard turn over issue?

After reading your post again, if the battery cable is getting hot I would start popping fuses until you find the issue.