1 - For a 20k chip lead by the first break you must have been playing waay too many hands.

2 - People that push all in alot do this sometimes to wear people down so when they go again youll call with a less strong hand. That being said, AK is an instacall.

3 - KQ is not a favourite vs AJ preflop. I know you didnt say it was, just reminding you.

4 - How are you sure your KQ is good at any stage. On the flop you may be behind many hands. He flat called your flop bet. Id seriously check any turn that isnt a Queen and see what he does. The turn can give him two pair, more possible trips e.t.c. Id have checked, let him bet or check here, then called behind. The river is good, AJ is unlikely, but id still bet alot less. Or even not at all. Read kingsnthehole's post about pot control and anything ive written about it for more ifno.

5 - Betting 6k on the flop and 6k on the turn is stupid. Bet in accordance with the pot. If the pot on the turn is now 20k, you have 24k back. You cant sensibly bet 6k as its too weak. So 14k+ is now the correct amount for leading out at this.