Mike,
I think it's important not to put the cart in front of the horse.
B y the way, what were the air quality results?
A mold remediation expert to get in there and resolve the condition will cost you a chunk of coin.

I think we all tend to get prematurely exited when we hear the M word......and no....not Marriage!
The sky isn't necessarily falling because of the M.
If it is Cladospoium, it is black mold, but not considered toxic black....however, avoidance should be mandatory if you have any respiratory weakness.

I'm afraid I couldn't glean much from that photo, but what I did see didn't APPEAR to be frightening. Looked to me like a very common sight in poorly ventilated attics, but it won't go away by itself. Mildew formation on the north sides of attic roof sheathing is common and particularly so closer to the soffits, if ventilation is being impeded.

Sprayed on Hydrogen Peroxide, according to mold experts I've spoken with is the sure fire cure. They have claimed that it is the most effective of all the mold disinfectants available and the least harmful to the human body. From what I've been told, it's the only product that will kill the sub-surface mold spores. Bleach is a complete waste of energy, looks like its doing something but NOT!. I encourage you do research the product more.

The thing is, this mold must be eliminated or encapsulated before any ventilation improvements are attempted.

The two most important things of course to be vigilant about, are personal respiratory protection and preventing any contaminated materials from entering your living space. I would be darn clear that you wear an appropriate respirator for this type of work.

The soffit venting you described is very commonly a sign that there will be attic ventilation issues. The 2 in. discs, do not provide enough airflow. What you've descibed equates to about 7 ft of strip soffit venting and even then I doubt that they would provide as much air. I think finding a way to get more air in from the soffits will be the big one for you and then maintaining a route for the air movement (baffles).

I am in agreement that the insulation adjacent to the affected area may require removal. Use lots of big garbage bags, and protect your living area.

Rick