What is the ruling on working for a company that sells forbidden things (munkar) and pork, knowing that my work is limited to selling halal food products, and I have no connection to the forbidden sales?

If your work is only in the permissible sales department, and you have no connection with departments that sell forbidden things, then there is no harm upon you. However, it is better for you to look for work in a company that does not sell forbidden things at all.