4. Why Does The Tardis Always Take The Doctor "Where He Needs To Go?"
The Tardis has been shown to be a sentient being with no problem expressing itself in the limited means it has at its disposal. From trying to avoid Captain Jack to "not liking" Clara, to disrupting the attempts of a salvage team to steal her parts, the Tardis is by all indications as alive as you or I. In The Doctor's Wife, the matrix of the Tardis is removed and placed in the form of a woman named Idris. When chastised for being unreliable at getting him where he wants to go The Doctor learns that the Tardis always takes him where he is needed. Why would the Tardis constantly be dropping someone it claims to love in circumstances that not only could, but have led to his death? What could possibly be its motivation? A possible answer may be found in Idris's claim that the Tardis "stole a Time Lord" to see the universe. With a shared sense of adventure, the Tardis could be taking The Doctor where not only is he most needed, but where he would definitely not be bored!
3. Why Was It Impossible For The Doctor To Retrieve The Ponds?
Even though the New York to which the Ponds were banished is inaccessible by time travel, what would stop The Doctor from traveling to New Jersey in the same year, taking a train to New York, collecting them and heading back to the Tardis and adventuring with the Ponds? Even if they needed to place a fake headstone in the graveyard and have Amy write her novel and have it published in the 1930s wouldn't it at least be worth a try? The simple answer is that the showrunners were done with the Pond's story and as with the death of Adric, no amount of timey-wimey jiggery-pokery could overcome that.