So I would have 10 ranks in density 10 in Immunity and 10 in Protection
No! You have to use the secondary points pool to buy ranks in the new powers, you don't just get 10 ranks in each one. You pick where you want to allocute the points. Maybe you want to be tougher so you buy more Protection, or heavier so you buy more Density.
Since the game is PL 10 i am limited to 10 in all those stats correct?
No, your not. PL does not limit the number of ranks you can take in a power (with a few exceptions).
PL specifically limits Attack Bonus, Defense Bonus, Toughness Bonus, Damage Bonus, Attribute Score, Attribute Bonus, and Skill Ranks.
For example, a normal PL 10 character has a maximum damage bonus of +10. The Blast Power uses it's rank to determin Damage so a Rank 10 Blast has a Damage Bonus of +10, the maximum for the character (unless he trades Attack Bonus for it).
However, some powers, like Regeneration, Immunity, and Enhanced Attribute don't have 1 to 1 parrallels. You can have 10, 20, or 30 ranks in Regeneration or Immunity because each rank is applied to a narrower focus.