I’m not sure of the exact options on the DS-260 but words like “clerk” and “assistant” often cover job titles and descriptions of people who handle the kinds of jobs that you seem to describe.
The key here is to be honest and present as much information as you can that answers the questions. If you don’t, that’s where issues come.
A big thing here is no gaps in your employment history. If you didn’t work for part of a period that they’re asking to know your employment history, say “unemployed.” Otherwise give details of the job.
Leaving out anything the form asks for (and mentioning things beyond what the form asks for) are unlikely to be helpful and could hurt your case.
This thread from a while ago should cover you pretty well in terms of what to expect. Some folks now getting their case number within the 12 weeks, but others still having to email after 12. Not sure of any rhyme or reason. After you get the case number, you’d just follow instu