"Kenmore" products are made by a number of different manufacturers each having several different designs of products. Posting the dishwasher's model number *from the appliance's model and serial number tag* will allow us to find out what particular appliance design you are having problem(s) with.
You can find tips for locating the model number tag on your appliances in the 'Repair Parts' section of my site linked below.
** Wondering if I seal the gap up will it affect the operation of the washer. **
Probably. If it is there, it is there for a purpose.
I would suggest you first try to isolate the cause before attempting to modify the design of the dishwasher. It could be as simple as a lime or scale build-up in the air gap that needs to be cleaned or replaced.