Bump after 73 minutes? Impatient, aren't you.
Your description of SH3Patrol is correct, and you should never need to delete any patrols, campaigns or anything else when you use it. Or even if you mis-use it.
The Corrientes counts as an 'ocean tanker' (ie, a tanker in the ocean, like a U-tanker).
SH3Patrol should be used in two stages:
1. After you have docked at the tanker: Go to the main menu of SH3, press ALT-TAB, run SH3Patrol, click (for Corrientes) 'North Atlantic tanker', click OK. Now return to sea. You will find your date at sea is now (randomly) 1-5 days on from when you docked.
2. After you have sailed away from the tanker, for at least 30 nm (I always use 100 nm), 'save-and-exit'. Return to the SH3 main menu. Alt-Tab again, run SH3Patrol again, again with 'North Atlantic tanker' selected (for Corrientes). Return to SH3, reload your saved career. When you have fully reloaded, check your Mission Orders. The grid will no longer show NULL.
This is very tedious, but there is no other way, owing to the way SH3 is hard-coded. Of course, you don't have to carry out both parts (1) and (2) above, if you prefer to skip part of the functionality to save time.
Stiebler.
NYGM Tonnage War Mod - Leading Edge Realism
[Also the most realistic and best-tested campaign files!]