Yup. This actually happened.

[Khalithar]

The 95% likely comes from the fact you have 95% of the required stats in the one stat you are lacking. The + likely comes from the fact that you have more stats than necessary in the others, so that would compensate.

Essentially yes.

Edit for clarification:

Using the level 35 mission Allied Maneuvers as an example, it requires 455/315/190 for a grand total of 960. Let's say my total is 160/160/160 for a total of 480 points, that's 50% of the required amount which should be a 50% chance of success in my opinion.