Ok, as someone who has done some extensive testing with this let me throw you a few pointers.
First, at any point during gameplay you can press the Score Window command which is the "'" (apostrophe) key. This will show you in a percentage from 0-100 how far along you are in your mission.
When playing the "Deployment" campaign you will not be able to progress to the next mission until your score reaches 100%. When playing the "Georgian Oil War" campaign anything over a 51% will get you into the next phase.
I recommend this; play the two missions that you need to play to get back to the one that is giving you trouble. If you're already at that point just skip to this next step. Go to dcsblackshark/blackshark/data/scripts/logbook and make a backup of your players.lua file.
Then, if you fail the mission again, just go back to the logbook and copy/paste the backup you made into the folder. This will revert you to your previous progress and save you from having to replay any more missions than you have to.
Next, select the mission and read the briefing pages very carefully. Once you know exactly what you need to be doing in the mission start it up. Fly to TP one, engage your targets, then press "'" to check your score. If it's 51% or greater press escape and quit the mission. If not just fly to the next TP, rinse and repeat until you get 51% or better.
What Einstein said about success being partially dependent on your allies is supposed to be true, but in my experience your actions effect your score to an exponentially higher degree than your allies actions do. Most of the time if you're able to eliminate all the targets at your TP's you'll get a 100%. On some missions I've gotten to 100% after only engaging enemies at one TP. I've also had missions where I killed every enemy at my TP's, spent another two hours engaging other random enemies and still wasn't able to get to 100%.
"Expect No Mercy"