Sorry to hear about the trials that you have been faced with, with your girlfriend and such. That sounds very stressful. I cannot even imagine.
As for the horse, let's see. Do you use a rope halter on him? This can be really helpful in transmitting signals a bit sharper and giving you more leverage due to the knots that kind of "bite" into the face if the horse resists.
When working with him , at first work in the driveway where there is no grass to tempt him. Ask him to stand away from you, and every time he moves, send a "flick" down the rope (you swing the rope up and down and a wave of evergy/movement passes down the rope and can snap the horse under the jaw) . Start small but if he does not stop what he's doing , get bigger.
His job is to stand there, so every time he does something else, such as move or reach down to eat, you snap the line at him (small to bigger). If he keeps doing it, you dont' need the small anymore, you go straight to one , quick sharp snap, and I use a "Ah!" voice scolding. YOu must do this every time , every time. And ask him to stand. When he's good for a few minutes, go in and pet him and walk off to a new spot and try again.
When you do this in the pasture, if he puts his head down to eat, dont' try to pull him up. Rather, you throw that wave of rope down the leadline at him and "interupt" him. The quicker you can interupt his thought to go down to eat, the easier it will be. You must watch closely and be super consistent.
Good luck and remember that if you have to, letting your horse languish a bit due to caring for your girlfriend is not anything to be worried about. He will be fine.