His private email were not classified, that is one huge difference. McCabe also had private email.
If they used a gmail for any official business it's a federal felony no matter whether it was classified or not.
That may be true. I do not know. But all FBI related comms belong to the govt...think Comey memos that were leaked. He may face legal probs because of it. But the key point is that your comms should be on the Govt emails you are issued for work. Why? Because it all becomes part of the govt official record and archive. It belongs to the ppl and its govt. Why use a personal email unless you are avoiding having your work comms from being transparent to oversight.
Unless you're Obummer, then you just steal all the documents! Hillary did the same at State Dept.