Ah! Glad you told me that or I would have been up all night long trying to figure that one out just the same as you
In that case, I'll call this mission "finished". It works. It runs for about the right amount of time. And I figure you have enough ammo to get through all the targets, so long as you're thoughtful with each shot, as you should be!
Maybe I'll make a bit more advanced version: A chance for a random submarine or gunboat threat during the day? And probably a few strategically placed SAM sites or MANPADS to make helo ops a bit more interesting and also provide some targets of opportunity to hunt for between fire missions.