I think, you can have a try. You can wear contact lenses first, then wearing your diving suits as well as lunettes. But you must make sure that your lunettes are well made and won't leak water to avoid water into your eyes. Since you are wearing contact lenses, if there also leak some water in your eyes, it may cause eye infection or other eye uncomfortable. So, be careful!
It is OK because there is the arm head equipment for you when scuba driving. You are near sighted. Only wearing the contact lenses in the common arm head equipment can you see clear. However, there may be the special arm head equipment with high prescription lenses for the near-sighted ones. If you use that type, you could wear no contact lenses.
Yes, maybe you can. Because most of the time you can dive safely with contacts. However, in repetitive dives, you can interfere with gas exchange over the surface of the cornea, and in some cases you can seriously damage the cornea as micro-bubbles form. Also, you should pay attention to the infection which can happen easily. Or it will damage your eyes. Besides, you can go and consult it with your doctor. He can give you a good suggestion.