The effectiveness of the doubleteam is calculated with respect to IQ, ATH, DEF & SB. Speed factors in as well (it really helps in generating turnovers) and fatigue level. The reason your doubleteam was ineffective is that you are starting 4 freshmen. The doubleteam alone really won't overcome poor defensive ratings, lack of athleticism, and unfamiliarity with the base defense. On the offensive end, you had all of your distribution focused on a perimeter player against a man defense. I understand why you did that, but efficiency is programmed to decline slightly when 1 player has too much distro compared to the other players on the court.
So, if you are going for quick development, you just need to suffer through. However, you need to adjust your practice settings for that to work. Gailey is worth starting, but with that 5 WE he will never develop much. Unless you have made promises that prevent it, you should put Terry back in the starting lineup at C.
Once you have a developed team, then my suggestion would be that sim-AI coached teams tend to shoot more 3's. You could control that by shifting your defense to the perimeter (say 2-3 at +2 or switch to 3-2 at 0 or -1). After all that, then you could doubleteam the "if leading scorer" on 2 guys, or "always" on 1, and you might see an effective result.