So I suppose the scope of this thread has changed significantly. I now believe my issue will only be solved by using a different method. I am still unsure why the OrderDtls method gave the 1000 SO limit response. I will create a new thread regarding my next attempt to add order lines with GetNewOrderDtl. I hope to see you all there!
I will update with a link to that thread once it is posted.
Edit: Continued my project here Create new order line GetNewOrderDtl CURL PHP