I think your bird needs more attention than 2 hours a day. Birds are flock animals and are within that group pretty much 24/7. Of course our lives generally do not work around the lives of our animals so we have to find ways to work around. I agree that 2 hours direct attention should be the minimum but they also need more attention less directly as someone else posted.
Mine are on a variable schedule, they usually get about 5 hours of direct or indirect attention from either me or my partner, sometimes this isn't possibly and they are lucky to get an hour but this is rare. Other days they will be out all day. This isn't anywhere near ideal but they have each other for company (indirectly) when we are out but it does keep them relatively stress free because they are used to expecting the unexpected.
I should start changing his toys before he gets bored, when an animal gets bored of a toy and it is taken out the next time the toy gets put back in they either remember they are bored of it or get bored of it more quickly. Personally I feel toys should be rotated a minimum of weekly.
Have a look on the homemade toy thread for ideas on how to keep your bird busy, give your bird lots of foraging stuff. The busier he is the less he should scream.
Try to predict when he is most likely to scream and try to prevent it before it starts. If he starts screaming when you leave the house then give him a bath right before you go, if he screams whilst you are watching TV then give him something to do before you switch the TV on for example. When he takes the bait then you can reward him for being quiet. Completely ignore him when he screams.