The "How to Win at D2 and D3" thread will be your best friend here. There's not much more from that thread that can be said that won't help you win. What others have said here s also true. Also, don't game plan yourself out of wins. Until you really grasp it, don't go more than +1 or -1 on your D.
As others have said, you need ATH in bigs, and SPD at guard, and good D. Your bigs have bad ATH. You've done well getting REB, but without the ATH, you are bringing a shiv to a gun fight. You run man to man, so you cannot take those 30 D guys. Everyone needs to be at least 25-30 points higher in D.