Thank you for your comments.

To turn off the fix for .acsm or any other extension, click "Enable/Disable Content Types". To adjust opening automatically vs. saving, try the steps in https://support.mozilla.org/kb/change-firefox-behavior-when-open-file

When you have a content type set to "Use [relevant application]" on the Settings page, Firefox 98+ uses the "Save files to" folder to save the file and pass it over to [relevant application]. Firefox 102 for Windows/Linux will have a preference in about:config to allow using the system Temp folder instead, similar to Firefox 97 and before (browser.download.start_downloads_in_tmp_dir).