Hmmm, this is a tough one. Major kudos to you for taking these guys on, and not just giving up on Christopher and handing him back.
This might be a place where a little conditioning might help, if you have the time and patience for it. Since you have already separated them in two separate pastures, you are in a position where this might work.
Take baby steps, to start with. Take Christopher on lead into Honey's pasture. Start out keeping him on lead, just let him graze or have a carrot in Honey's pasture, just like 10 minutes at a time. Reprimand any bad behavior sharply and put him back in his field, but make going into Honey's field a good association. Praise or treat him as long as he acts calm, grazing and not acting mean towards Honey. The minute those ears go back at her, snap that lead up and take him back to his pasture, don't fuss over him in his own pasture, make sure the daily 'good things' he gets are always associated with being around Honey. Work your way up to taking the lead line off and letting him graze or whatever for 10 minutes, always supervised, and always quick to end the activity at the first sign of churlishness he exhibits towards your mare. Don't walk away or leave them together unsupervised for some time - not until you are sure you can trust him. Each time he is showing signs of success, reward him and then up the ante - give him and Honey treats side by side, pet them together, etc. Horses are creatures of association, it might be a bit of a long process doing it this way, but it should work. He will likely always lord over her a bit, horses will always need to sort a pecking order out amongst themselves we can't really control very much - some horses are simply more dominant natured than others. I think the idea of putting a bell on him is brilliant - she can defend herself a bit better when she knows he is coming.