Good Morning Amy,
It's been awhile since I have heard from you. I hope things are going well.
The group you are trying to create is a dynamic group. You are NOT able to remove contacts from a dynamic group.
However, with that being said.
You CAN.....
Highlight everyone in the group (highlight the first one, hold down the shift key and hightlight the last one)
Once they are highlighted, right click in the blue area and choose "Add selected members to a new group"
The Query Builder window will come up.
Name the Group and click on OK.
You have now built an AD-HOC group of the same contacts. You can highlight any individual and right click and remove that person from the group. You can also access this new group from your Mail Merge.
I hope this helps.
Have a great weekend!!
Dale