I didn't see all of the video (slow download!) but this is what I think:
You don't look so bad. You do need to develop your riding, strengthening your core, working on developing an independent seat.
Your horse doesn't look as though he's fighting YOU so much as he has trouble balancing when his head is held in. At the walk, he can manage--he seems like a nice, kind horse-- but when you start to trot--especially when you lose your own balance a little-- he needs his neck to help himself balance.
I'm not an expert or a teacher, but I'm wondering if you most of your riding in a circle? To help both of you, I'd actually forget about any kind of frame, just keep a nice contact, and keep working on brisk forward gaits, and do these exercises: change of direction (as in serpentines), leg-yielding, and transitions (they don't need to be abrupt) because these exercises will automatically supple and engage your horse, and you will improve in riding them.
And of course I recommend lessons, whenever you can!