Yes until you have adjudicated the other charges, the state can add them on. There is some authority for double jeopardy if you pay the tickets before they file charges. I would consult with an experienced traffic attorney in your area ASAP
Is it possible to be charged later with a DUI? Yes. Is it likely to happen.... NO. I cannot speak for other counties, my practice is pretty limited to Cook and Chicago. However, for the most part you are in the clear for the DUI charge. As to driving... You are legal to drive at this point. The tickets act as your license during this time period. What is important now is that you make your court appearance and get disposition on the tickets that will not effect your license.
The breath test you were given at the scene is a PBT (portable breath test); it is generally only admissible in court to establish probable cause for an arrest, or reasonable grounds to believe a driver is under the influence. Failing a PBT ususally results in immediate arrest for DUI. Since that didn't happen here, you likely passed. Although legally you could be still be charged, it is highly unlikely that will happen at this point. You can drive on the tickets until you get the DL back. Hire an experienced traffic/defense attorney though to handle the tickets: the first is a mover and the second will have costly consequences on your auto insurance if not handled properly in court. Most of us will provide a free consultation to you. www.galivanlaw.net