When you make the decision to change an unwanted behaviour your dog is likely going to exhibit the unwanted one more persistently for a period of time.

He does this not because he is fighting for leadership in your home but because the behaviour was successful in getting something he wanted. The behaviour worked.

Pulling to get to the tree; jumping to say hi; barking to make the scary thing go away.

You are changing the rules of the game when you decide to remove reinforcement for the unwanted behaviour. 

The behaviour which was once successful isn't working anymore. He's frustrated. He tries even harder to get the result. Barks louder, jumps higher, pulls harder.

He will do this until he realizes it no longer results in what he wants but the new behaviour does.

For you to be successful you first need to set him (and you) up to succeed. Have a plan which includes 1) what you prefer 2) how to get the behaviour 3) how to reinforce it 4) how to prevent the unwanted from being reinforced 5) what will you do if it doesn't work.