Yes, he can. If the case is "enhanced" with the prior offense, his potential term of confinement is up to 1 year in the county jail. He should also be aware that he can lose his driver's license for up to two years and that he is not eligible to receive a driver's license or occupational driver's license for the first year of the suspension.
DWI 2d conviction requires at least 3 days in jail as condition of probation, so expect some jail time. it is not unusual for DA to demand at least 10 days, but seldom more. The delay in processing his case is not unusual, but you should see something happening soon. For more information about DWI 2d, check out the link below.
Yes, he can be sent to jail; but he may be able to schedule his jail time around his work schedule so that he can keep his job. Generally local attorneys will know the sentencing habits of his particular Court. I recommend that he contact a local attorney as soon as possible.