The 1st agent you spoke to is obviously totally incompetent . If you skip the 1st leg, your entire itinerary will be cancelled.
If you want to skip the 1st leg, you need to cancel proactively your ticket and rebook CDG-ORD at whatever price will be available at time of rebooking, very likely much more expensive than your original ticket. When cancelling the existing ticket, you'll have to pay 50€ change fee/ticket and the miles will be re-credited to your account(s).
I have the feeling, reading your post, that you want to do that because feeling uncomfortable for only having 2 hrs for the connection. If this is correct, 2hrs is totally sufficient to make this connection.