Fold this. You have position and good pot odds, but you have a very bad hand for the situation. All of the hands that he is 3 betting for value have you dominated.
You're getting 3:1, (275 to win 805) and against AT+, 99+ you're barely 15%. Add in KJ+ and you make it to 30% but when you consider reverse implied odds it's an easy fold.
Moral of the story: You're not getting 'great odds' against a 3-betting value range with weak Aces.
No really happy about opening A7o this early. When the tourny is deeper you should open up, but for now it's not bad idea to pass up on your A7o, especially if you feel exploited by these 3-bets.
It's all tournament and opponents-related. You actually won't get any generic rules about how to behave in different circumstances. It depends on a stage of the tournament, stack sizes, skills of the other players and your previous history with them.
In your spot it's easy fold and it will usually be, and what I can suggest is not to open too wide with the Ace/rag, because it's not profitable in the long term, unless you are sure that you have good reasons to do it.
It's much different than Ax, but it also depends on a villain. Against the nit I'll fold it and against any decent player, but not nit, it's a call. If it's aggro 3-bettor, than 4-bet to 1100/call.