UCC25600: Explanation about Gate Voltages

Hi everyone,

i desined an LLC resonant converter and i'm attemting to optimize the gate voltages of the Half-Bridge MOSFETs. 

I have these questions:

1. Why does the gate voltage decrease during the on time? Is it because the pulse transformer is not working in DC?

2. Why is there a voltage spike during the "dead time"?

3. Why is the 10kOhm resistor ncessary between Gate and Source? The gate capacitor discharges towards the diode and the inductor winding. 

Here is a typical gate voltage acquired with the oscilloscope between Gate and Source. 

Here is the schematics of Gate signals. 

Thanks,

Best regards.