This is stressful timing, but it helps to separate what you actually know from what you're fearing.
"Routine security review" is exactly that for most people. GMAC triggers this fairly often with online exams when anything unusual happens during the session -- and a camera adjustment during the whiteboard portion is the kind of thing that can do it. It doesn't mean they think you cheated. It means their system flagged something and a human is going to look at the recording.
In the vast majority of cases, the review wraps up within the 20-day window and the score stands. Score cancellations do happen but they're the exception, not the norm.
On the application side: don't wait. Submit your applications now. Most deferred MBA programs are familiar with this situation and will work with you. I'd email admissions at each school briefly -- something like "I recently sat for the GMAT Focus and my score is temporarily under routine review, expected within 20 days. My previous scores are 645 and 655. I will update you as soon as the score is released." That's transparent, professional, and gives them context without oversharing.
Your score trajectory (645 to 655 to 675) actually tells a solid story. You've been improving every attempt. When the 675 clears, that context will work in your favor.
Reach out to GMAC through official channels too just to keep a paper trail. Most people in this situation end up fine -- try to take it one step at a time.