I think you seriously underestimate how seriously Mikheal takes this Issue.
I understand that Mikhael takes issue with backing down from this fight, or rather any fight, but these are the kind of events that establish a character. Situations change, and people grow. I think being hit by a train like HB could go a couple of ways for Mikhael, personally. The cause of this being that Mikhael wouldn't back down might cause him to be more conciliatory in the future. Or, the whole experience could drive him into a self-propelled Derse shattering frenzy. It's all up to you, as his player.
In any case, this is a thing that is happening. There will be situations where fighting is not the best course of action, or even close to the best course of action. In the future, it would be wise to keep this in mind. If meta-gaming keeps your character participating, then a limited amount is acceptable.
For now, it is important to keep in mind that, as far as HB is concerned, for the moment, you are more valuable alive than dead, and he will most likely refrain from killing you outright. Unless you
continue to antagonize him after he drops you to zero hp.
Anything you want to do with your turn other than attempt to make yourself mobile? You are prone and can't move, but a second wind is still an option.
Hmmm. Can I scourge Charge through the Imp to the gate?
Not through him, but if you hit and kill him, then make your full movement, you can be one square from the gate on your move. Or you could take an opportunity attack and double move through.