Would you be so nice and share some Mid-Side tips to give “life” to a mono lead vocal (using your Har-Bal AIR feature)?

By definition, a mono track has no side component so mid-side processing can do nothing for you. All that you can do is to stereo’ise it using cross-coupled ambiance to simulate a space. In Har-Bal 3 using about 50% air should do that pretty well.