Yep, ViaBTC would have been a good lifeboat if the tx would have been smaller. Maybe you consider making smaller batches in the future (just an idea).
Any chance for people to start doing CPFP for some of those transactions? (Probably not, unless they are getting desperate).
Yes the free service for ViaBTC acceleration will not work due to size and even the paid service is something that I don’t think will be cost effective, because most of all this paid accelerators are expensive than regular transactions fees (although I don’t know of this period)
Also the CPFP will not be visible for any of the receiving addresses because of how high the fees will be when trying to cover up for the parent transaction