Your design is poor. You will always struggle with it.
If you want additional options to show in the two combos, you'll need to add them to tbl_Check. Keep in mind that if the two combos will have a different list of options, you will need a separate table for each of them as you have the app designed. OR, you will need to manage the value lists on the form which is just poor practice.
Not that it will help you unless you are willing to rethink the app, but I've included a sample mini-app that I include in all my apps to use to manage all simple lookup lists.