Lump of wood and a hammer and whack it ...
If you undo the seat back cover at lower edge you can then put a torch under the cover and see the retaining spring clip inside the headrest tube, using long nosed pliers grip the left side of spring clip and pull it to the right and towards you at the same time the clip then comes out allowing you to pull headrest out without using force, (other than when rusted in),the spring clip can then be re-located before pushing headrest back in ...
It's usually rust that makes them tight ...
Depends on your height and body shape ...
If you're tall with long legs and arms then Mud Rails or equivalent will move the seat up and back giving a more comfortable position (assuming no bulkhead).
A previous owner may have had rails fitted to the passenger seat to raise it ...
You can test your changes by packing your seat up with washers ...
if still no joy, try altering the pedal height ...
