That is a very concentrated DNA reaction. Normally, in 30 ul I would react 200 ng of DNA. The nominal reaction is 1 ug in 50 ul. This is 5x more concentrated. I'd recommend scaling back the amount of DNA. Using large amounts of DNA and little or no water is in general a bad strategy, as the DNA is concentrated (with columns or precipitation, or whatever) in combination with undesired contaminants, such as ethanol. Diluting the DNA also dilutes these contaminants, and can save you from many problems. If I wanted to digest this much DNA, I would do it in a 300 ul reaction, not in a 30 ul reaction.
go ahead and dilute the DNA.... gels should be able to detect up to ng levels of DNA so dont worry. Use the NEB cutter and choose other enzymes since the interval between the two sites is too short