Warning. Just my 2c worth, I have dabbled withis, but I am not a cmprehensive expert.
IMO, Your best bet is to export your data into a format that Moodle can import. See http://docs.moodle.org/22/en/Import_questions#Moodle_XML
I suspect I know the issue here: you have a nice database solution that enables you to create questions quick. It's the link to Moodle that is missing. With care you should be able to create an direct export from your M$Access that can get sucked into Moodle.
But, once you see all the new bells and whistles Moodle has to offer with questions, you may want more and newer and different types of questions.