I was going to suggest taking some measurements on the pot but, without doing testing on my own, I can't be confident that the motor controller would work like I expect. I would hate to give advise that could cause a malfunction and hurt someone and/or damage equipment. A picture of any of the labeled terminals on the motor controller could help in determining what options you have.
You should have everything you need for adding analog out card. Before you do anything with adding I/O (or anything else for that matter) make sure you do an IMAGE backup. I learned this the hard way.
Setting a program as a macro makes some minor changes to how other programs can call it and puts it into another category for easier sorting. It isn't something that is needed. It also lets you assign it to buttons and menus that can be run without being called from another program. I use macros to control things that are specific to a particular robot cell. I then call these macros for the main part programs. This lets me run the same program on multiple robots even if the cell setup is slightly different. I write protect the macros so they don't get deleted from the controller by accident.
Hope this helps