Need to Merge a single page PDF into every other page of a multi-page pdf

Yes, this can be done using a script. You would need to use the insertPages method in a loop (I would do it from the last page to the first one), insert the new page after each existing one.

If you're interested, I've created a (paid-for) tool that allows you to do it very easily and quickly. You can find it here: https://www.try67.com/tool/acrobat-insert-one-pdf-file-into-another-multiple-times