Hi Neil,
I have no ill will towards you, and appreciate anyone trying to make an honest, entrepreneurial dollar.
With that said, you're handling this situation with Bradley like a real douche.
My advise (take it or leave it), is start acting like a professional. Treat your potential buyers with some respect. Stop selling the same car twice. Stop listing stale/sold cars all over CL (weeks and months after they're gone). Stop representing cars as 'for sale by owner' when you don't actually own them (and have never even seen them).
Most importantly, stop forcing buyers to 'unpeel' the truth from you. There isn't anything inherently 'sleazy' with using insider access to flip cars. The 'sleaze' is coming from you, and it probably speaks more to your inexperience than any dishonest intent.