Hi,
As you said, two line items at sales order in which one is delivery related and another is Billing
So you can control this in the Item category VOV7
For the service line item, make the Billing relevance as B ( which states it as Order related Billing and status according to order), you can leverage ITEM CATEGORY TAD
For the Delivery line item, make the Billing relevance as A ( delivery related item)
standard item category TAN can be referred
And based on the item category your schedule line category will follow which will be
Service item you can use CD ( no delivery)
Delivery item you can use CP
just go though VOV5 and VOV6 settings of standard and revert if you need any further clarification
regards,
santosh