Do you want those boxes to be pdf form fields? That is, when someone opens the PDF in Acrobat or Reader they would be able to fill in this form? If so, you’ll definitely want to use frames instead of a table cells. (However, you can anchor the frames inside the table cells, which can help you with the alignment.)

We have a bunch of articles on PDF form fields on the site here.

What happens when you export as IDML?
Did you try rebuilding your preferences?

Well, I’m glad you found that solution. But it does not do Smart Text Reflow. But maybe you just meant automatic flowing (flowing from one page to the next). Smart Text Reflow is slightly different:
https://creativepro.com/make-indesign-add-pages-automatically-as-you-type.php
I don’t think that is possible with two threads. But maybe I am wrong! :)

Not really. Perhaps the font file is just corrupted. Maybe try to get a clean one.

I would check to see if it’s just this one font or all fonts.
I would try rebuilding your preferences. https://creativepro.com/resources/faq
And check to see what keyboard setting you’re using in your OS. Perhaps you or someone changed it from US keyboard to Greek or something like that. (April Fools Day was this week!) :)

I doubt that this would be possible. Maybe with a custom script?