Nolehoe,
You are correct in thinking that 100g of loose T7 should yield more velocity than 100g of T7 pellets. I can't explain the louder boom or the greater felt recoil, but here is my explanation for your change of impact.
The velocity of the projectile traveling down your barrel probably was slower with the "pellets" load which means more time in the barrel, which means the barrel has more time to recoil up before the bullet exits the barrel, which means a higher point of impact.