I strongly recommend consulting with an attorney. Misdemeanors are not anything to sneeze at.
1. The crystal ball is out of service.
2. Unless you have legal counsel as to the impact of pleading otherwise, always plead not guilty.
3. If convicted, yes it is forever. No expunction of actual convictions in Illinois.
4. Who knows. It's possible, it's public information. I found out my son had been arrested for shoplifting when I googled him to look up his mailing address.
5. If you are indigent and can not afford an attorney, you can ask for a public defender. Public defenders are not some default for those unwilling to pay for an attorney. You can get one if you qualify by asking at your court date. They will assign one (there will be one "on duty" typically there). You case is sure to be continued at that point.
6. Fine can be up to $2500 and you could also get a year in jail (unlikely).
Other advice? Sure. Consult an attorney. Many counties in Illinois also have Shoplifting diversion programs. If you can get into one of these you will take some courses and do a period of probation but if you succeed you will avoid a criminal record.
In addition, the store may also independently send you a demand for damages (unrelated to the criminal charge).
The cop is not responsible for screaming or lecturing. The judge may do that, still (well not scream unless you act like an ass in court, but I've seen plenty of judges lecture).

