I see several things at work here. First you seem jealous that he got the supervisory position and you didn't, so you may be misinterpreting what is going on organizationally as a personal attack when it is just the nature of adding a layer of management. Managers are privy to more information than the people below them. That is normal and expected. It is the supervisor's job to decide what needs to passed down and what does not.
Next you are under the false assumption that your supervisor is still your peer. He is not. He is your boss and it is up to you to adapt to his working style not the other way around. This is not to say you can't discuss things with him, just that he has the final say and you are stuck with that even if you disagree with his decisions. He is more organizationally responsible for the success of the project than you are, so he has a greater stake in the decisions as well.
Now a third factor may or may not be at work here. The guy may simply be a snake who has gotten ahead by making himself look good at the expense of others. If he doesn't care about team work and is only out for himself, it is hard to change this type of person. Time will tell if this is so and you would then have to decide if it is time to move on as these types of supervisors are generally not helpful to your own career aspirations.
But what to do to handle all this. First, yes he is your boss, but you need to talk to him privately and honestly about your frustrations with the information flow. He may think he is protecting you from being bothered and not realize how much it is frustrating to you. Make a list of the problems and your proposed solutions before the discussion as it helps you to make sure that you make all of your points. Try to do this professionally and not emotionally. Yes this upsets you and yes you are probably mad, but getting angry about discussing it will only backfire.
Next when you need information on a particular topic, ask for it in an email which gives you documentation that you asked (in case he does turn out to be a snake).
Then adjust your own attitude. The best way to get promoted is to make this guy look good and getting him promoted. Give him your all. Support his decisions (the time to discuss is before decisions are reached not after) and do your best to make the project a success. Fighting him as part of a "competition" (hint, you are no longer in competition with him as he is at a higher level than you are) will only make you look petty and reduce your chances of winning promotion yourself.
Finally go do some reading on how organizational politics works. If you want to get ahead, you cannot afford to not play the game.