How did you come up with the idea to migrate a big shop to Prestashop 1.7? Why not at least move to a mature version like 1.6? Anyway, not my problem!
Did you deactivate the HTML Purifier in the shop settings? If not, give it a try.
But even then I doubt that 1.7 can handle such a large amount of inline css. Hopefully 1.6 does.
And btw this is a user forum. Bug fixes are always welcome here, but this is not the right place for bug reports. ThoseThose belong to Github/prestashop.