Regarding your questions:
1) Unfortunately, because of the nature of the integration, there is no way to make those fields editable. VirtueMart actually doesn't have any direct "link" or "view" into the form option fields or the values. That's all handled in Breezing Forms. What we've done is allow a VM2 custom field to point to code that inserts a form, and then captured the shopper choices as final text values. There would be no way to have them become editable on the backend within VM2.
Now it is possibly feasible that a particular shopper's form choices could be edited by creating a custom UI into the Breezing Form database, but that would likely be prohibitively expensive for something that is needed only rarely by a store owner. Also, eventually VM2 (or VM3?) will have much improved native custom fields capabilities and support order editing, according to Max, which will render the Breezing Forms Custom Fields integration approach obsolete. So it doesn't make sense to expand BFCF to support this through a non-VM2 editing feature when this is an "interim" market solution.
2) I would think that you are onto the right answer with echoing details of the order in the payment plugin. Your payment methods would need to be customized to pick up the information but it could be done.