If you mean nicely fixed as a bad thing that doesn’t happen.
As with riding you don’t concentrate on the front. The side reins are loose. They don’t pull the head in. It doesn’t happen in the first time you lunge him.
You concentrate on the hind end and getting that working. The reins you will see a difference on day 3. As I said you need to be taught to use them and what is the correct length.
I am afraid I am too far away to help you.
As for - he throws his head up and you drop the reins. As I said horses learn from release of pressure. If you put pressure on (pick up reins) he throws head. You release reins you have given him a release of pressure. Voila you have taught him to throw his head.
Also if throwing his head is a dangerous thing then you are in the realm of danger I spoke about with teaching him to rear.
If he doesn’t know any different then reins mean turn and stop. Legs mean go. To apply them at the same time to a horse that doesn’t understand is confusing. It is a confused horse that throws it’s head, rears, bucks, spins, etc.
It is a skilled rider who teaches a being that doesn’t understand English that they can mean other things.